Is it also laziness that brits don't pronounce the r in water?
No, it's the accent. It has nothing to do with laziness, it's just how people grew up speaking.
Which brits? There's a lot of us.
I dont know how you can't pronounce the r in water. Otherwise you're just saying "wort".
im not familiar with that phenomenon.
Also, I'm happy to say that an accent can come about from cultural laziness towards pronounciation.
Which includes actively avoiding key syllables to words.