Well, I think there are priorities! If you're trying to save people's lives then yes, 'arts' takes a back seat. And tbh isolating is quite often a useful part of making art, so lockdown didn't necessarily preclude that.
To you, they may have been just 'arts'.
To the artists, they are their livelihood.
A great many people working in the arts were PAYE Freelancers (so unable to claim either SEISS or furlough), or Limited Company Directors (so unable to claim either SEISS or furlough), or had gone self employed after April 2019 (so unable to claim either SEISS or furlough) or had more than one job in the years they looked at for calculating SEISS, even if they had gone full time self employed in the arts since then (e.g. in TY2018/19 deriving 51% of your income from a bar job and 49% of your income from being self employed in the arts, but your career was taking off and you went full time self employed in April 2019 - you'd be unable to claim either SEISS or furlough).
Artists retreats are a thing, yes. To avoid the distractions of everyday life, and focus. But it's really very hard to focus on creating art when you're in a state of terror because you've been banned from working, given no financial support, and are in great danger of being made homeless because you cannot pay your rent. That's not an artists retreat, that's enforced poverty.
You may view the theatre, art galleries, live events, craft fayres, weddings and suchlike as frivolities that we can do without. You would have a very different view if that was how you paid your rent and fed your kids.