Because it's not a good feeling hitting them and they'll always make you think whether you're blowing out your tires or fucking with the suspension.

Around me, they're either 2 inches below the road surface, so a giant pothole, or 2 inches above the road surface, so a giant speed bump.

When I went to Mexico, none of them had the covers, just holes everywhere on the roads and sidewalks.

The manhole covers are lava!

I drive through a new area near our home everyday (in UK). Some of the manhole covers make a loud "clonk" noise when I drive over them. I avoid them because it will otherwise annoy our new neighbours. I used to live off a main road into town. There was a loose manhole cover there which drove me crazy until I managed to get the council to fix it. Probably just had stones in it making it loose.

After freezing temperatures, construction, and deferred maintenance, manhole covers can be a damaging obstruction

My car is only two years old, and the one time it needed work …. I hit one of the smaller pieces of road infrastructure - a gas valve maybe. But the pavement was broken up around it so it was a deep hole with a sharp metal edge. It destroyed my tire, a damn expensive tire

At least up north around where I live manhole covers are often also either holes or bumps in the road due to things shifting around from the freeze/thaw cycles. Basically potholes with a purpose. Hitting bumps is bad for your car, so that's a pretty good reason to avoid them. Though I'd never swerve around a bump if I was going to come close to someone else, since that's much more dangerous.

Because I drive the same way every day. I know which ones to avoid and which ones are fine. I also have to pay to do maintenance on my car. If I can move the steering wheel a few inches for certain covers rather than spend a weekend replacing suspension, I'll do that.

My favorite people are those who drive giant SUVs with huge tires lifted way off the ground who do this and also slow down to 2MPH to go over train tracks.

Tell me, what alignment is your car?

In my city, they just keep paving over the old asphalt, so the manhole covers are like 6 inches deep in some places. Hitting one of those in my sedan is not pleasant.

Same reason I don’t let my foot hang out from the covers. Also that icky thunk thunk.

Why do I feel good when I avoid stepping on the pavement cracks?

As others have said, it's just not great for the car. Will it damage it if you hit one? Probably not. But if it's your work route or other commonly taken route, you're gonna hit it 260x in a year, and you'll own the car for multiple years. It adds up quick. Plus, they aren't always smooth to the ground or free of other pot holes and square edges. If you hit it hard enough or if it's too sharp, jagged, or deep, you can damage the wheel, the suspension, and the tire itself, easily in the thousands of dollars to repair, along with not having a vehicle for up to a few weeks.

Don't get me wrong, they shouldn't really be swerving all over the road, but dodging em when you can is nice.

As someone who opens them regularly, because so many of the chimneys are collapsing and I regularly wonder how some haven't caved in yet.

The forces on your suspension can be tremendous. Repeated impacts cause faster wear. Large impacts can cause immediate damage and/or loss of control. The popularity of large wheels means the capacity of the tyres to absorb an impact is reduced, and even with larger sidewalks, tyres can be damaged by impacting a sharp edge. A single OEM rim can cost over $1000; a suspension repair is probably in the same cost range. At this time of year in frosty countries with failing infrastructure, manholes aren’t typically even close to level with the road surface and may be a significant road hazard.

Jeeps have the handling characteristics of a jeep, and hitting bumps in them is uncomfortable. “Off road capabilities” is not the same as Baja.

It's fun to do on a motorcycle.

I would try to avoid driving over them when safely possible, because they make an annoying noise, which I wanted to spare folks living nearby from. ¯\_(ツ)_/¯

Your tire usually drops into them and this shortens the lifespan of struts, ball joints, sway bar links, control arm bushings, and potentially throws off your alignment.

Because it feels horrible to drive over and if they're bad enough you can crack your rim on them

i unconsciously avoid sidewalk grates also. fear of falling forever ig

In addition to frequently being a dip in the road, there are two on my way to work that make a clunking noise when I go over them and I don't like it. This has lead to a habit where I just avoid them in general.

I don't expect them to fail, it is just the noise and bumping feeling.

I drive a small car with stiff (sport) suspension. In my area manhole covers typically aren't aligned well with the road surface making them quite bumpy to drive over. This can jarring and even painful for me due to medical issues that I don't care to get into here. So I routinely avoid driving over manhole covers.

I find the name manhole to be sexist and I prefer the term personhole.

I know which ones near me are bad.