Why I think it is wrong is something to do with believing that I do not have the right to have things just because I might want them.
While it might be harder to think of a large company like Tescos working to have things available to sell, they do put in money/time/effort to get products to put on their shelves.
I believe that labour/enterprise/effort should be supported, so if a shop has made/grown/purchased an item (or a person in their own home), then they can choose to exchange it for cash & I can choose to take them up on their offer because we have chosen cash as our method of exchange.
For this to work, we both understand that they own the item until I give them the thing they are willing to exchange it for, when it becomes mine.
So, they won't take it back after I've paid for it & I won't take it from them if I haven't paid for it, and nobody else will take it from me (in a law abiding society where people don't steal).
Because we uphold this system, shops will take the time to source products that I might like/want/need to buy which I might struggle to get without them.
e.g. I could never get a banana if shops didn't import them as they don't grow in this country.
I can make shoes, but only if someone lets me get the tools & materials to make them out of & I have the space & time to do it.
I'd rather pay someone else to have the tooling, materials, knowledge & skills to make shoes for me.
While in theory I can make/grow what I would need to survive, I would prefer to have the option to purchase many things that require specialisations & use my time in other ways.
Without a society wide belief/contract that I can own things with little fear of them being taken from me, or that a shop can own things with the same security, nobody would risk having those goods or would have to guard them like every banana or pair of shoes was the Crown Jewels.
The ability to trade is an important social contract that supports a society where people can specialise (so we all get nicer bread/shoes instead of being at the mercy of how good a baker/cobbler we might or might not be) & ultimately lift up all citizens.
Scientists can spend time working out how to cure diseases or heat homes efficiently instead of making their own shoes.
Farmers can develop methods to increase yields & feed more people instead of trying to make tyres for their tractors etc...
I believe that some of being part of a successful society is based on following certain rules such as not stealing, which should lead to a better, safer society for all.
So it's a 'for the greater good of society' in general over what is good for me right now sort of reason, which overall is good for me as it creates a society that is safer & better for me to be part of.
Ughhh, that feels like really muddy thinking & I will probably end up spending a week thinking about this.