Earlier quoted context omitted.
> and some don't have a credit card If your customers are from Europe, it's not some , but most customers that don't have a credit card. Credit cards are uncommon here (probably hard to imagine if you are from USA). Online payments are a fragmented mess in Europe. Most countries have their own preferred online payment method (like iDEAL or bancontact), Paypal is basically the only reliable method that works everywher…
> If your customers are from Europe This is not a great approximation. In the UK you can assume almost every person has a payment card that works on the internet (debit and/or credit). In Poland on the other hand, the number of systems gets silly ( https://m.lot.com/us/en/payment-methods-on-lotcom )
WRT. your number of paying systems, note that there's exactly one Polish payment system there - DotPay. Every other system there is to support other countries (not surprising, given that you've picked up the site of the national airline).