The thing is, Sheik plays an aggressive Defense. Most of Sheik's defensive techniques consist of making Sheik's aerial approach unpunishable or punishing others' approaches, either of which can lead to a tilt combo. Sheik's defensive advantages consist of the following:
1) Needles. Fast-firing, hard to dodge, disruptive projectiles. If your opponent is not approaching, you can charge them, and get even more of a disruptive edge out of it. They are great against some comon tactics. For example, if your opponent is prone to shorthopping an aerial at you, landing out of grab-range, and back-rolling before you can retaliate, a burst of needles will catch them out of the roll and pin them, setting you up for an approach
2) Downsmash. It comes out instantly, has high priority, and multiple hits. If your opponent shields, there is a fairly large chance it will shield-poke with a late hit, and if not, it will knock them out of retaliation range. If they spot-dodge, it will catch them out of the end of it. As Sheik's Fair, Nair, and Bair are essentially lagless, you can downsmash immediately upon landing when performing one of these moves, and it will catch an opponent who tries to shield-grab, or further pressure their shield if they hold it.
3) Uptilt. Instant, huge range, huge duration, high priority, great setup on the knockback. Protects Sheik from most aerial attacks, especially from above.
4) Bair. It can be used to hit outside of just about any grab range.