Why would a 74LS14 be used to enable another IC?
It seems your circuit is incomplete or got pins mixed up. It is extremely unlikely that outputs of the 74ls14 are used with the input being open.

Using a schmitt-trigger circuit when receiving clock/enable like signals to improve noise immunity is quite sensible. As the 74ls14 is inverting, connecting two inverters in series to remove inversion is sensible and common. Thus it seems like you miss the A3 input. Finally while the delay is small, it might be sensible to make sure that the clock or enable signal arrives after some data signal or further control pins. The propagation delay through two schmitt triggers might well be enough for that.