Indeed many people thinks 2FA as 2 devices. I am not sure where that came from and what specifically make people think that way. Despite all my research and experience using 2 devices solve no specific security problem. I think there is a whole topic to be argued on this (should I make a blog post on this?).
As for me I have Aegis on my smartphone (really perfect nothing to say). But I have many unwanted/unnecessary 2FA to go through every day (for the last 3 years). I am cleaning my cookie/connection every time I close my web browser and I am not keeping my computer on all the time. Therefore those 2FA needs to be done a lot (I mean at least 3 time a day). I do not interact much with my smartphone, also this is the least secure device I own so web browser extension is an OK way. I used to have a python script I could have run from one of my IoT through ssh. So far I don't see any vector of attack this would prevent compared to browser extension.
I see hundreds of thousands of users using other extensions that I wouldn't run on my system and I am sharing a better solution, nothing perfect, nothing that requires mass adoption.