Bits don't weigh very much and fit in a convenient laptop shaped carrying case.

It also has the advantage of working the way I expect when I want to do the things I use it to do.

Do containers do that?

That's a tough question to answer because you haven't clearly stated your requirements. It makes it very easy for you to prove that something doesn't work while making it very difficult for someone else to prove it does.

What I meant about configuration is that the onus is on you to manage all of that. I know some people love that level of control but most people it's a burden. Containers are part of your profile and move with you if you're using Firefox Sync. You don't have to copy or maintain multiple profiles or Sync accounts.