I don't disagree. My point was, to take a simple example, at places like Booking.com [new] people will typically find out about the used CPAN Date classes from

I don't disagree. My point was, to take a simple example, at places like Booking.com [new] people will typically find out about the used CPAN Date classes from the code or their table neighbour. Not by rolling their own or crawling all of the CPAN before finding DateTime. But sure, the internal code will be a bigger issue.