It is like sales tax in the US. You busy charge it to the customer and good. Everybody selling there pays is, so why bother?
Yes, but let's be honest let them charge their residents sales tax and VAT. They are all mature people that can leave it they do not want to pay. It course they don't. But not because they are lazy but because they like the subsidies︀ that their VAT pays for.
OSS is good, you only register once and pay once.︁ Much less overhead than having to register in all countries.
Of course not paying would︂ be most interesting but I guess this isn't an option anyway. They want it, they︃ pay it, we collect it for them.