Tile can complain about Apple stealing market share all they like but the main reason for changing from a Tile to AirTags for me was customer support
I have had many Tiles, even before replaceable batteries, buying regularly. I had upgraded to a Tile Mate with a replaceable battery and after a year, it ran out and I popped in a new battery. No quibble. Less than 3 months later I got a 'low battery' warning on the Tile. Weird. Popped it out and put a 'reputable brand' in instead, just in case the cheapo first one off eBay wasn't up to scratch. Same thing, died 3 months later. I therefore deduced there must be some issue with the Tile. Contacted Tile support. After a week or two of waiting, I got an email back saying that the product was out of warranty and straight away, they said the only thing to do was to buy a new one - oh and here's a 10% off link. Felt like a real slap in the face, at least do a dance about 'Oh have you tried resetting etc' so that I can feel like the product is actually dead. 10% off is also not great. Was told if I wanted to be sure in the future I would have to subscribe to the premium subscription.
After that, I decided I would be milking this one until the AirTags came out - they seemed to not care and just be hungry for an extra sale. It's been an ok device, sometimes needing me to run around the house before it'll 'connect' (and I live in a relatively small house) but the locking of 'premium' features behind a paywall that seem to just be functionality they should include initially got me annoyed and this lack of real service finally put the nail in the coffin.
TL;DR: Tile Mate was just out of warranty and Tile did not give any support, only gave me a coupon. That and locking of features behind a monthly subscription makes AirTags a no-brainer upgrade