It really depends on what Zelda game you are playing. If I'm playing Loz then you definitely need one. Taol very important. Alttp I use it a lot. Oot I rarely used it, mostly as a child. MM I think I did only against Deku scrubs. Wind waker, I use the shield more then My sword. TP I didnt really need it, SS it was only useful when fighting cursed Bokoblins
I've never been terribly good at the combat in Zelda, but I do always try to use the shield if the situation calls for it. I know you don't really ''need'' it in most situations, but it's fun to use and it feels ''right''.
The only time I seriously use a shield is for all of the older console/handheld games and SS. Mainly because in those games, the shield can be very useful and I'm bad at hitting projectiles with the sword(SS).
I'm one of the rare ones that go out of my way to find ways to use it. I can't explain it and it doesn't seem very logical, but there is something satisfying about blocking rather than evading. I guess that's just my style.
I always keep it around for looks, but I do love using for combat. It's an excellent counter move and easier to attack an enemy after they hit your shield when compared to a side jump or backflip. It does take skill to use the shield wisely.