Don't forget that Tech Supplies payments are handled by a third party, WorldPay, part of Royal Bank of Scotland, so they control what they accept and Tech Supplies has little control over that except in changing payment handler.
I can certainly think of reasons not to like PayPal ( as buyer, seller or payment handler ) but it seems WorldPay has decided to accept PayPay so that may filter down to allowing PayPal payments through Tech-Supplies.
WorldPay can accept American Express and other payment means but sellers have to decide on whether any particular payment method is good for them or not. There's a lot more to it than simply getting money exchanged for goods, particularly when it comes to fraud, dispute, fees and general legal and commercial issues.