Because the cheapest new iPhone is $600 and you can get a cheap new android phone for around $100-$200 and get 6 years of security updates (Galaxy A16 for example)
If a smartphone is no longer a computer where you can install whatever you want, why bother investing so much money on a very locked-down phone? You can use the hundred of dollars you saved to spend on a small portable PC or something to run any software you want.