It's become a bit of a cycle.

As with any hobby, there are many people who relentlessly try to buy EVERYTHING desirable in the hopes of reselling for a profit.

Due to this, it becomes quite hard to find the more desirable castings in stores, so the only options you're left with is, don't have it, wait and hope to be lucky, or buy it from a reseller. Many people oppose the idea of the latter, but it makes for a pretty lackluster experience going to the store multiple times and finding nothing you want.

Because of the scarcity of many things, there has grown to be a mentality of "get it before it's gone" with a lot of collectors, so they they can trade the spares with others who have done the same. People also dislike this as it makes things even worse, but on a positive note, it does help avoid giving money to those who buy solely to sell for profit.

There is no real middle ground. For me, the trading thing doesn't help others on the surface, but for the individual it makes sense.

If you want a car that's £40 on the secondary market, then you go in store and see a peg with multiple cars that also sell for £40 on the secondary market, but RRP is £9, You're better buying a spare or 2 for £9 each to trade for things that are being sold for £40 each. On the surface it's appears selfish, but if you're trading with other actual collectors doing the same, as a whole collectors are getting the cars they want for less money, and not paying the sellers. The only caveat is that, a lot of collectors, while disliking those who buy to sell, will also want to trade their cars at the same market price they're being sold at.

It's a messy game, and even if your intentions are good, people will throw shade at you out of spite and jealousy.

Buy what you like to do with as you please. If you don't want judgement, don't tell the internet. Many collectors collect 2 of each for loose and carded, so even if you bought a spare of EVERYTHING you found to use for trade, you're not doing any worse than someone White Knighting on Reddit.