Was me. With >500 Capts and >500 FOs on the fleet, and doing, say 100 "trips" a year (trip varies from 1 to 5 days), you might see the issue
Wondering if any airline ever came up with the idea of forming small teams within their crew pools who fly regularly together. Human beings work best in groups of up to 30 people - part of our evolutionary heritage.
Not knowing your colleagues in the cockpit may be seen as advantageous or at least convenient by the airlines, but I don't think it leads to a high level of well-being among the crews. You'll probably find that your conversations with your colleagues don't go much beyond the basic introductions, as does your familiarity with each other.