Like most discussions, obviously we all talk about things from our own experience and our own circumstances.
As a parent who paid for all of their dc to have swimming lessons from when they were 4, school swimming lessons were a complete waste of time. I never objected or anything, but my dc were able to walk up to the baths from their school, and my dc were more than happy to have a swim for 30mins and that was just how it was. I would have baulked at a demand / request to pay £81 for them to do that though, as I was already paying for lessons for them.
However I have taught in schools where, when we took them for a school swimming lesson, that was the first time that some of the dc had ever been inside a swimming pool. I was shocked the first year, but it was quite common (to the extent I devised some pre-learning about the sounds and smells and getting changed and storing your clothes whilst you were in the pool, and we used to get bowls of water and get the children to practise putting their faces in the water, blowing bubbles, etc before we even got to lessons, as it meant they were a bit more prepared when they started.
For those children, going swimming with school is important, however much this is a shock to many MNers who don't seem to be able to perceive that there are families who have never taken their dc swimming, and who have never taken them on holiday.
Unfortunately, of course, there is likely to be a correlation between schools attended by pupils where the majority haven't had swimming lessons, and the schools where parents don't have "only £81" spare in their budgets.
I don't know what the answer is, as no Government in my lifetime is likely to fund all schools to the level they need, or the level that would resolve issues in schools. Even if there were a massive boost to schools' budgets, if anyone put me in charge I would start by funding SEND support properly, not subsidising a coach to take all children swimming.