That's because of Bitpay.....any invoice can be paid with BTC or BCH. Bitpay were in the big block camp and when the BCH guys hard forked in 2017, they added BCH support fairly quickly, probably hoping it would facilitate adoption.
Not by default anymore. Merchants now have the option to select whatever coin they want to accept. BitPay pushed BCH in your face initially, but later made it an optional feature. I guess that Roger was too demanding there. Merchants accepting Bitcoin don't want to accept something else alongside it, which may lead to bad marketing.
If not for Bitpay, I doubt there would be much merchant acceptance at all. For BSV, it's obviously even worse. I really have no idea how the forkers convince themselves to stay the course. Their coins are on a long, slow bleed towards zero.
As long as Roger and Jihan are willing to devote their BTC mining earnings to financially support BCH, BCH will remain up and running in the top 10.
BCash has actually very little organic transaction activity. It's way less so than Litecoin with orders of magnitude less merchant adoption. They artificially inflate the transaction numbers, and artificially inflade the on-chain value volume by moving insane amounts of BCH back and forth. How pathetic.