I almost always waveshine before heading up into the air at low percents. I usually try to waveshine in the direction I think they're going to be knocked back. The reason is it gives you a split second to read their DI to follow up, and by waveshining in the direction you think they're going, even if you guess wrong and they go the opposite way, you still have time to chase them with a DACUS/nair/Dash Attack instead of being in the air throwing out an aerial the wrong way. Especially at low percents, following with a waveshine gives you more options than jumping into the air. For example, if they get knocked back close to you you can do things like waveshine>jab>grab or waveshine>JC waveshine>anything else. If they get thrown up high enough in the air, you can easily follow them into the air with a shine or any aerial. If they DI away from you, you can dash after them and use a JC shine/Dash Attack/nair. If they shield, then there's a good possibility that you'll end up waveshining behind them to punish their grab. Also, learning to waveshine onto platforms especially will net a HUGE improvement on your combo game, as well as general movement.
But everything depends on the situation.
So yeah, waveshining is amazing