Is it rude for a driver to not speak to customers?

I've been taking Uber rides for a couple years now, something like 200 rides with a 4.96 rating. While I dont think drivers should be forced to have a full conversation with someone, I do think they should at least have common courtesy + manners.

I greeted my driver, but he didn't reply. Didn't even look at me either and he was staring at his phone

And he did understand English, as he picked up a phone call a few minutes into the ride through bluetooth speakers.

When we reached my destination I said "Thank you sir" and once again he didn't say a word to me.

I give 99% of my driver's a 5 star rating and a $5 tip unless it's a very long ride. But sometimes I get drivers like these and wonder if they really deserve either of those... what do other drivers think?