Sorry if my question was worded badly. Obviously, some people are playing games in the browser - perhaps I should have asked more specifically what the appeal is, e.g. is it mostly small casual games like what Flash used to be used for, or do people actually play more invested games?

And sorry again if the answer to these questions is so obvious to some of you that the question itself sounds dumb, but I'm simply not experienced with this topic.

Running games in the browser provides a bit of convenience of not having to download and run a platform-specific executable. There might be some security benefits too.

Depends on the nature of the game though. It works best for games that are lightweight and stateless.

Sure, this was clear to me too. My question was not so much about the advantages of browser games but rather if they actually have a market.

And speaking of that: what are the main monetization schemes? Are browser games sold like other games? Or are they mostly ad-based like other web content?

As one data point: https://itch.io/games currently lists 729397 games, 844 of which are tagged HTML5. It's nonzero but I guess it's not that big. But https://itch.io/games/html5 lists 301816, I am not sure how to reconcile these numbers.

Some of those are accepting donations, but I can't tell if they are profitable.

Browser based games are huge (often with kids). A lot of of popular games cluster on .io domain names. Shell Shockers has been a big FPS:

https://shellshock.io/

And there is a whole genre of multiplayer things eating things to get bigger:

https://agar.io/

http://slither.io/

Yes, lots of people do. Not as much long story based games, but more arcadey/casual games. This is especially common for kids using computers at school. Just think about all the old Flash games, that style of game is still popular.

Lots of indies like to make their games available and easily playable (e.g. no download) during development on itch so for that use case, yes, it's important.

That sounds cool and interesting - so, the idea is to eventually sell the final product as a stand-alone game, but target the browser for development versions from the same source code?