My work profile has uBlock Origin with stricter rules which would break some sites/tools I use for work. I also redirect Twitter to Nitter, use a different password manager, etc.
For bookmarks, it's more a question of not wanting to have personal stuff together with work stuff. Then there's some settings that works on one profile but would cause issues (or annoyances) on the other. I also have a different theme for each profile, which stops me from doing personal stuff on sites with my work login (eg: searching on Google).
I also have a profile that is just for the shittiest sites I sometimes find online. I'll have extensions to block the crap, archive pages, etc, which would slow down browsing or break most sites I use.
On Chromium, I had one browser and 3 profiles. Then I decided to move to Firefox and since using profiles (especially switching/opening them, at least on Mac) is a pain, I use 3 different browsers (Firefox, Firefox Dev/Beta, Waterfox) as they all have their own profiles.
Could I live with only one profile? Yes, but that would force me to compromise. Containers alone? I tried to use them, but stopped after searching for stuff on Google and YouTube on the container I had my work Google account logged in. Profiles + Containers are the best of both worlds in one plane.
> but stopped after searching for stuff on Google and YouTube on the container I had my work Google account logged in
Thought I'd mention though, that this is one of the areas I find containers a life-saver. Google's handling of multiple accounts is so badly broken, that I only ever log into a single account on a single container. Easy to keep work and personal Google separate then.