In Europe and UK, an ATP is only required for those flying as pilot-in-command (i.e., captain) of a multi-pilot airplane for air transport purposes.
In the US after a crash in 2009, ATP or R-ATP is required for all scheduled air transport flights, but that is not all commercial flights. Ironically, that crash was flown by two ATP holders and so this requirement change would not have helped.
In both cases, a CPL is a prerequisite for the ATP (ignoring military hacks and some MPL stuff).
Hmm? You can get instrument rating with CPL. There's also non-passenger commercial pilot jobs - cargo and agriculture for example. Those CPL holders are, by definition, professionals, even if other professional take the ATPL on top of their CPL.
But yeah, there's a lot of pilots.