are 3 links even worth it?

im curious mostly for items like twyzle and such, like items that give a buff but only to socket gems, and can only contain 3 sockets at most, it seems like the trade of 3 sockets for one good buff isnt really an even trade.

for example why would i ever use a wand that is limited to 3 socket instead of a bow which can go to 6?

You get at least one 6-link regardless of build - your body armour. That's all you need in almost all cases. Your links after that are usually going to be utility stuff that doesn't need heavy support. Of course there are exceptions, but they're not super common.