I think it is normal to look at least decent when going shopping especially to nicer stores. Running grocery shopping is different but I would personally not go into a store wearing sweats (except I once when by car in running clothes and shoes to a grocery store but that was a nice outfit too albeit sporty). I think that we should respect others by dressing up to the occasion too, not meaning fancy necessarily. However, I am European and in Europe everyone dresses up more, I also lived in CA for 9 years and no one here would go out to the streets wearing sweats and slippers. Here in Europe they also judge you by the way you look for sure, which is often wrong of course.
That said jeans and flats and clean hair and decent skin but not necessarily made up and done hair should suffice too in my opinion. Accessories do dress up a person more than anything else, that is very true. Wearing an expensive watch or piece of jewelry, a pair of nice shoes or a nice bag is often enough. Even though they might think it is strange and I would not do it myself because I would not feel comfortable, I think there is something trendy about someone dressed up in a quality jogging outfit and one expensive piece and mixing styles and/or price range works. All depends on the person.
SAs are, however, most often trained to judge customers when they enter the store to assess whether they are likely to buy or sadly here they are often not trained at all and would have no clue if someone is wearing an expensive watch for example.
On the flip side I only once visited an LV store locally and was treated very badly. At that time I was wearing a casual short suit, heels, had my hair done and makeup on. I promised myself to never return or buy anything there. I went with the intention to buy and when asking questions they told me to look online and decide, like how am I supposed to even try on the bags online?
I shop at Burberry next door to LV and even if I only go there twice a year, they greet me by name and treat me great. They also often compliment me on my outfit even if they are not designer or not their brand. All depends on the SAs but when going for an exchange or return I would probably dress up a bit more to receive respect for sure except if you are a return, well-known customer like I am at my local Burberry store.
He just isn't concerned about commission, oddly enough. I mean, he likes it when people buy stuff but he also just gives me tours of things even when I tell him up front I'm not buying anything that day (he knows when I say that, that I mean it).