Breweries & Bike Shops: Navigation -> Search -> POI Categories ->

I wonder how the POIs in Europe get there.

Garmin used to charge people extra for maps and people never paid for updates after that initial purchase.

Garmin uses OSM because it reduces the cost to the consumer and because OSM has more cycling-specific features than their "City Navigator" maps (which are more for automobile use and which they charged extra for).

Cyclists would be better off updating routes and paths on OSM than updating POIs. Having accurate roads and paths is much more important to the primary purpose of the device and it's a much more attainable goal than POIs that keep changing. I'm a regular OSM contributor and I don't bother much with commercial POIs.

If people are regularly looking for bicycle shops on their Garmin, maybe they should be paying more attention to maintenance. That is, looking for shops is more likely to be an emergency thing. If people can find them on the Garmin, it really doesn't matter how they are categorized. Having more information about the shop (like when it is open) would also be fairly important. If you have cell access, looking this up on your phone is a much better approach.

The categories might be due to how the data is organized in OSM. It might be more work to recategorize things than you imagine. Given that the people will tend to use their phones, it might be a lost cause to spend much effort in improving it. Searching on these small devices is always going to be a less pleasant experience than just using your phone (whether or not one uses Google or an "offline" database).

You are more likely to be looking for "brewpubs" than "breweries" anyway.

Looking up "brewpubs" is kind of odd anyway. The likelihood that there would be any in the immediate vicinity would generally be very low. If anybody were really interested in such a niche type of eating establishment, they'd be better off doing research before their trip than they would expecting to find one that was convenient.