Why British carriers could not always launch an alpha strike

Why could British carriers not always concentrate for one large alpha strike?

They often had to provide continuous fleet air defence before and after a strike, so aircraft could not all be committed at once without exposing the force.

The appeal of a decisive alpha strike had to be balanced against the British requirement to provide air defence across a battle that could continue for days. A larger carrier concentration at Cape Matapan might have launched a much heavier opening attack. Those same carriers, however, had to keep fighters available before the strike and continue protecting the fleet afterward. Sortie generation, offensive mass, and continuous defensive cover were parts of the same carrier-warfare problem.