The reason why some games/sellers are not using PayPal as a Gateway is because how easy it is to charge-back your payment.
Paymentwall have other gateways such as MINT, banktransfer, Mobiamo (mobile payment), Ukash, paysafecard (pretty popular pre-paid card for games).
As first time buyer in Pipiload, didnt had any bad experience with them as they always takes their time on 1st time buy, rest went smoothly.
I always make research on new sellers who I have'nt heard anything about just in case they can be extremly slowly, asking alot of personal information without any good reason ect