There's five of us and we've always fitted our stuff for SC trips in the boot under the load cover.
That's great that it works for you but.... folk are different. We holiday in Norfolk and Yorkshire, which we all love, but I wouldn't dream of telling others that there's no need to think about going abroad, just because we don't.
I did say about putting it under a tarpaulin if storing outside, or maybe one of those green outdoor covers that they do in a range for everything from collapsed rotary driers to motorbikes - just to protect against light. That said, plenty of people (as on this thread) leave them on the car permanently - quite likely not in a garage - (does make me wonder why they don't just get a bigger car!) and they seem to survive intact. Thick black rugged plastic storage boxes designed for outside use tend to be just fine in all weathers, unlike the clear crates designed for indoor storage.
If storage is the concern, you can get huge collapsible bags designed to go on the car roof (affixed to the roof bars, like with a standard rigid box) and also, endearingly, car 'ruck sacks' - the same, but you strap them to the back of the boot! Obviously not as robust as the plastic ones, but maybe a useful compromise to consider?
As a slight aside, I only recently learned that the stated maximum weights for loading on car roofs only apply for when the vehicle is in motion - for travelling safety - but the roofs can often actually bear much more weight than that. You can get custom-designed roof tents for appropriate vehicles (typically minivans or estates - probably not a Beetle!) that two people can sleep in, along with a load of their stuff, sometimes up to about 500kg-worth!
you really don’t need much, esp if you buy stuff there
I get the basic reasoning behind this, but surely it's not always that simple? For food and things like toilet roll, yes, probably; but who wants to spend a day or so of their holiday traipsing around unfamiliar shops in unfamiliar villages, maybe with an unfamiliar language, trying to find all the stuff that they need for a reasonable price - stuff that they already have back at home? Isn't that how you end up with 12 footballs in the first place?!
Even at home, knowing all of the available local and regional shops where they all speak English and state UK sizes/specs, I'd still struggle to buy much of what I want/need without the internet, with a minimum 1-day wait for delivery. Plus, unless you're only buying consumables in the exact quantities that you will use up, don't you have to either bring it back anyway or wastefully throw (or give) it away again at the end?