[piombisallow]

Why would they not think it's from the same word? Foresight, hindsight obviously come from 'sight'.

[noworriesnate]

Beware = be + ware, but most people don’t use be- as a prefix anymore (“I’m going to bequiz my students this morning”) and they don’t use ware to mean pay attention anymore. The word “sight” Is still in common usage though.

[bradknowles]

No, but there is still common use of the related form “wary”.

[KingOfCoders]

It's like you don't think of a window when you hear Microsoft Windows, or an apple when you hear Apple.