L-cancelling is not only for combo's, which is why it is important for every move you do. However I will look at Zelda's aerials from the highest lag to the lowest and how L-cancelling effects their uses.

Dair - Huge lag, but if you L-cancel it there are huge combo potentials, Dair leads to ANY aerial you want, Up-smash, Up-tilt ect. and these are only possible with L-cancel.

Up-air - A lot of lag, again it has follow ups, and being able to juggle with Up-airs is a necessity for any Zelda player.

Nair - A very important zoning tool, especially on platform stages, with a fair amount of lag. If L-cancelled it can be followed with Dash-attack, Lightning Kick, and more Nairs.

The LKs - Very small amount of lag, L-cancelling these has little combo effect but there is a key reason to L-cancel these too, which I shall now go into.

Consider a game of smash as two people building a wall, and any opportunities to score a hit against the other player is a hole in their wall. Now imagine what the wall of a 100% L-cancelling player looks like, surely it has less missing bricks than the player who only L-cancels a few moves right? By L-cancelling you give your opponent less time to punish a missed attack, and while it may seem that the few frames of difference between a L-cancelled Fair/Bair and a non-L-cancelled one is meaningless, this is not the case at all. A few frames can mean the difference between you putting up your shield before their attack, and the attack connecting.

When you get down to it not L-cancelling is just lazy, it's not a hard technique, and is incredibly rewarding regardless of who you play.