That's because a robovac enables you to clean super frequently. The marginal cost of vacuuming and mopping with a robovac is 0, so there's not much reason not to schedule it to run every day (or night if your model is quiet enough) so you can have spotless floors every day. I set mine to run vacuum and mop at 5am every day so I can wake up to freshly mopped floors. There's no way I would ever want to put in the required amount of daily cleaning to achieve that if I didn't have a robovac. The dock empties the bin, washes the mop, and refills the water tank through the laundry room water spigot as well as pumps the dirty mopping water out the washing machine drain tube in the wall so it's fully automated and I only need to rinse the water filter every couple of weeks and change the docks vacuum bag every 6ish months.

If you don't have any desire to have floors cleaned daily or to automate that then it makes perfect sense to just do a weekly cleaning like you do, but if you want to have 10 hours of cleaning done weekly then a robovac/mop is great for that.