Try going into a Home Depot. I don't think I've ever found one where aside from fairly near the front I've had other than 0 or 1 bars, across a variety of phones and carriers and in neighborhoods where the signal outside the store was strong.

The net is telling me this is because of the aisle after aisle of tall metal shelving and the building itself also has a lot of metal in the construction.

It is quite annoying when you are trying to use the Home Depot app to look up something.