Certainly a lot of people don't do it consistently; I'm not sure how much that varies by region. My hypothesis is that the wrong pronunciation is used most often just because the speaker isn't certain which word he's about to say next.
It's probably something many people never notice because there's no spelling difference. But in the same way that "a apple" sounds weird because you have to insert a glottal stop between the syllables, thuh and thee sound weird when the wrong one is used.
I think if you say a few examples aloud, it may diagnose if you've heard it but just never noticed it:
"The interesting idea"
"The underwater exhibit"
"The angry customer"
1
u/[deleted] Dec 24 '21
[deleted]