The ceilidh band that I play in does a range of gigs, from high-end, well-paid gigs to freebies for charity. What cuts across it all is this one fact:

The venue may ask us to produce evidence of PAT testing and can refuse permission to play if we don't have it. Simple, eh?

No argument - whether it's "work" or "fun" or whatever, the venue has its rules. If we want to play there, we observe them. So it's worth getting it done. Quite apart from that, we make every effort to make sure our gear is safe. PAT testing is an offshoot of that - and just another part of being in an organised band.