When I took up bass I started by buying a five-string because I wanted the options of notes lower than low E, and of being able to play low E to G# higher up the neck, and I didn't want the confusion of starting with a four-string and later moving to a five.
In practice I don't use the B string very much, but I very much like having it available. On the odd occasion that I pick up a four-string bass I can play it but it feels awkward because I'm not used to it.
Regarding "weak" B strings, I've never really had a problem with the way the B string feels under my fingers, but it does have a different tone - how different depends on the quality of the instrument. (But then, even on a four-string bass playing notes higher on the E string gives you a different tone to the same notes low on the A string, so...)
As for whether every bassist should play a five-string instrument, of course not. Play whatever works for you in your main musical style(s).
In practice I don't use the B string very much, but I very much like having it available. On the odd occasion that I pick up a four-string bass I can play it but it feels awkward because I'm not used to it.
Regarding "weak" B strings, I've never really had a problem with the way the B string feels under my fingers, but it does have a different tone - how different depends on the quality of the instrument. (But then, even on a four-string bass playing notes higher on the E string gives you a different tone to the same notes low on the A string, so...)
As for whether every bassist should play a five-string instrument, of course not. Play whatever works for you in your main musical style(s).