The problem is no company is going to pay you to get a PPC done as a captain if you can't be a captain.
The PPC as a FO used to be enough to obtain the ATPL, but now companies will be expect to pay for a candidate who is not eligible to be a captain.
When you apply to be hired as an FO, you are eligible to be one. Yes you need a PCC/PPC, but you are legally entitled for it.
Not the case with a the ATPL.
Also, MANY people work for companies with PC12 and other airplanes that are NOT a two crew airplanes, yet the insurance require unrestricted ATPL for captains positions. How do you expect those captains to obtained that? They can get an ATPL with ICAO restrictions, but like I said - they won't be able to fly to the US or Europe or even list a US alternate on their IFR flight plan, which is very restrictive.