Why would I ever cast True Strike?

One of my players has complained several times that True Strike is a useless spell. The effect of True Strike is:

On your next turn, you gain advantage on your first attack roll against the target, provided that this spell hasn’t ended.

His argument is that casting True Strike takes your action, preventing you from attacking, but attacking twice without advantage is better than attacking once with advantage, since you still roll twice but there’s also the chance of hitting twice. This is obviously true, especially since you have to maintain concentration until your next turn to get any benefit out of the spell at all.

So why would you ever cast True Strike? Is it just a useless spell?