It seems like noise, but there is the real possibility that people will start to lose the notion of politeness towards fellow human beings in general. Probably not adults, but kids will over time. So, no, it's not useless.

We humans tend to be very prone to getting offended simply because we can't really know what others are thinking, and we use defined manners to reduce unintended insults. We have seen this with email; over time, we are defining ways to reduce offending others by using emojis and other means. Manners are super important to help us work together so losing manners is a real problem.