Paypal routinely blocks payments of users they don't "like"
This could be adult content producers, software producers that the US government doesn't like ,and even people who raise too much money via a charitable drive or cause using a personal account.
If you did try to use Paypal, Slsk would end up having their money seized by paypal and probably wouldn't get it back.
I don't recall Paypal ever being an option, but I could be mistaken, it may have been once a long time ago, but in the last 5 years or so, it hasn't been an option, and not should it.