And they do, okay!
For example, my heels? Yes, by themselves, they are simply pretty. They are also a very hardy sandal-type design, which make them ideal for wearing them most places. The heels are one-and-a-half-inch wedges, which are stable and allow me to run in them if I really wanted to. They are also elegant enough to match any outfit I feel like wearing with it, formal or informal. These things, in themselves, don't mean anything. However! When I wear them, it means I am attempting to look aesthetically pleasing according to current beauty norms which tell me that wearing heels gives my legs a longer line, makes me walk pertly which translates into a dose o' cute, and renders me acceptable in conforming to many ideals of femininity.
This is a very different situation altogether than if I wore Tevas (which are a kind of walking sandal; I'm not sure what the big deal about them is, but apparently they are Very Good Walking Sandals), which I guess I effectively stole from my mom, because she doesn't use them. I don't like wearing my Tevas regularly! They're hard to get on and off in a jiffy, although they are great for long periods of walking. So, I generally use them for hiking at Gasing Hill. Now, I could use my running shoes, which are also perfect for such exercises, but my dad favours the river route at Gasing, so instead of soaking my nice Adidas pumps trying to avoid water, I wear the Tevas and slosh in the river at will. The running shoes are used for, obviously! running! Because that is their purpose, and I shelled out $200 specifically for a good pair of running shoes that I could run in. Which means, if I am wearing my awesome running shoes, you better believe I am going to do some serious running in them.
When I'm going somewhere informal for a bit and don't feel like wearing my very informal Tevas, or my informal heels, I am going to wear flipflops, which I think are my mom's. These say that I really couldn't be arsed to pay attention to my feet.
These are not "just shoes"! They each serve a purpose, and they each communicate something about the state of my being at any given time.
However! It shall now be noted, that these meanings apply to me, personally, and could be very different for you. For example, I have friends who have one pair of sneakers they use for... everything they can wear sneakers to. This doesn't necessarily mean they are careless about their appearance as I would be communicating in my choice of sneakers. Maybe because they can't afford other pairs of shoes. Maybe to them, footwear is just not as big a deal to them as it obviously is to me. Maybe they are communicating something about their personal aesthetic. I don't know! Because I do not always feel the need to interrogate my friends on their choice of shoes.
So, back to the main topic, folks! It's never "just [a thing]". This is aggravating as all get-out, and people on the internetz should stop using it as an argument.