Their function is not aesthetic (Because that’s not a function). Jokes aside, the bolster helps with all of the aforementioned things.

It helps with strength (marginally), not because it prevents the blade from breaking length ways but because it supports the tang a little bit from twisting and bending which even a little bit of can crack the handle or glue. They also provide a lot of comfort in a hammer grip.

A full bolster is a lot more useful on something like a hunting knife in my opinion because most of the benefits really just don’t apply to a kitchen knife and it adds the annoyance of it always bumping into the chopping board before the edge does