In a shop I can browse through the wares much easier. I can examine them, look at the size and specs, feel the weight and texture, get ideas.
More often than not, crucial specs of the product I am looking at are not available. Dimensions and weights are often missing, I often can't look at more than 5 or 6 articles at the time.
Webshops are great when you know exactly what you need. They are hell if your need is "4 or 5 buttons that would look good on that fabric"
The guy with a million kinds of tape can help you find a product that does X and Y, but won’t Z and matches your color scheme, the ukulele shop owner might recommend one that fits you or your style.
You could probably call around and get similar advice, but the places offering this kind of advice aren’t going to have free overnight shipping either.
I ended up trawling a few local plumbing supply stores and was really surprised how few washers they had, about the fourth store had a few random open boxes they let me rummage through and we agreed a price. It was unexpectedly difficult.
I've found similar problems getting screws I want (for a ceramics kiln). Gave up and used the best thing I could find in Screwfix (which aren't that good).
If you have the store to find mid-century burnished widgets at, people might regularly come from a hundred or more miles away when they really need just the right sort of widget, and when they do -- if your stock lives up to the hype -- they will tend to be big customers, buying a lot (since they weren't casually dropping in), being fairly price insensitive (since they have few alternatives for what they need), and repeat customers (since you seldom end up needing a specialty item once).
You might still need an online storefront, or you might take phone orders from your regulars, but the clientele of a specialty shop is radically different than the clientele of a generic shop, which relies more on people wandering by and which competes with ten other stores a mile away, and the big box store off the highway.