I used to notice this back in the days of NCL-LHR-TIP return being booked into full fare Y. Then my first long-haul being in B for NCL-LHR-SIN-SYD-BNE.

Now I'm rather blasé by it all - it's all based on the needs of the clients and it's not my money and still too hard/pricey to even do a fare difference upgrade to the next cabin as the cheaper buckets are sold out by the time I get to check-in desks.