The 90 days ROI might only happen if the price of bitcoin increases. It is not the same as before when the price reaches around $15k-$19k where all mining hardware has 3 to 5 months ROI.

There's no specific reason why others still mining bitcoin with ASIC miners, either they want to contribute to the network or they believe that the price of BTC will increase. Like what happens last year if you remember the price of bitcoin it dropped a lot around $3k last January 2019 so if you already have mining hardware before you already made a profit and already reach your ROI.

Since the block halving is already done there still a possibility the price today is not final and it can be still increased more than $11k just like what happens every block halving in the past.