[DSMan195276]

Seeing chess bots play as fast as possible isn't all that interesting - play gets better the longer they have to think and the more resources they have to use. They could potentially do what you're suggesting, but unless they buy a bunch of new/better hardware the play would be worse because the engines would get less real time to calculate their positions, which defeats the point. And even if they did get better hardware, they could keep doing what they're currently doing and get better games due to the increased hardware.

Basically, you're asking why they're not playing blitz instead of classical - it's just fundamentally a different format.