Stable coins are the most recommended for service payments.
I understand your sentiments, and you also have a point, Stable coins like USDT for example will prolly be better if the corporation is looking for stability to an extent, but in this case with Pornhub, I think privacy is their concern atm and not a coin with a stable network, and it's not so difficult to understand why they want to offer their customers some privacy looking at the service they offer, not a bad one, but not generally accepted by many; so I'm sure that's the reason Monero is being adopted by Pornhub.
There will be a massive acceptance for crypto in no time, bitcoin, monero, other altcoins. As in almost every possible accepted crypto. A huge volume would come in and demand for it.
We're already in a situation such as this, Bitcoin is now being adopted amongst traditional institutions that people thought wouldn't consider investing in a cryptocurrecy, not to talk of incorporating it as their reserve asset; as many altcoins that continue to work and develop their network, they are going to move high as well with Btc, since they all serve different purposes, some stable coins, others privacy coins, some used for low fees, etc, people can accept and use them all, as long as they don't turn into shady networks.