It's due to the nature of social interactions in India (more broadly, South Asia).

In most of our native languages, we don't directly address someone by their name, unless we've been acquainted before (sometimes even after, if it was just a formal acquaintance). We add a little something for politeness and respect. So it's always 'firstname'-ji or 'lastname'-ji, for example, in Hindi.

Since there isn't a direct carry over for this in English, people adopted sir or ma'am as replacement.

That's more or less it. It's about respect when interacting with someone else.

You'll notice that people who have been brought up in or are more familiar with western culture don't really do this.

EDIT: Unless ofcourse, your question was regarding the accent. In that case, most south asian written scripts lack certain soft tonal pronunciations of English alphabets, so most conversions result in hard sounding words, due to which you get the characteristic Indian (or again, more accurately, South Asian) accent.

Not sure about the colonial mindset or the caste practices of centuries but Indian culture is extremely hierarchial in almost all facets of life. Elders, seniors, higher officials, etc all expect to be respected even if it is just one year difference, etc.

One of the ways to show respect it to not use names and call as sir,madam, teacher, officer or at best elder brothers/sisters for college seniors. All this works well in the regional languages of India but sounds weird in English.

Directly calling names of elders is still seen as bad and if needed would use their name appended with sir madam uncle aunt etc.

This is less practiced in IT field in my experience. After years of schooling and college calling my teachers sir and maam it was hard to shake off the habit. A few of my managers had to remind me a bunch of times to call them by their name and not as sir / maam in the beginning. Even then I avoidedcallintg out their names and just started speaking to get their attention. Now I almost call everyone by name by default in office setting. It is still fun when freshers join and are asked to use names of 15+ year elders and them wondering if we are joking.

Just tossing a guess, would love for someone who actually knows to chime in though: in their language they're probably taught to refer to strangers with the respective word for "sir" as a formal construct, so they apply the same to English even though the culture is different, because they will probably be taught this way as sometimes happens, school teachers don't actually pass on the cultural uses/ways of talking of the countries where the language is spoken alongside the language itself, so it's easier to stick to plain translation in some cases