Originally Posted by yellow77

The only cities mentioned by the OP were PNS and LRD, which both have only ERJ service from IAH for the random day I checked.

Most carriers have some system where if you fly 25/50/75 or 100K miles on their metal, you get the lowest/mid/top tier elite status. For example, if you fly 50K miles on any revenue AA domestic fares, you will be mid-tier, no matter how you bought them or how cheap the tickets are (so long as they are published fares). They also have a parallel system (EQP) that rewards the purchasers of premium tickets, but they do not punish exclusively discount-fare flyers. Same for UA. Same for NW. Whereas if you buy cheap fares on CO but not from CO.com, you could fly as many as 49,998 miles without becoming elite. (You'd need to be very unlucky and never fly any segments less than the minimum mileage credit, and only fly cheap fares, but it's possible.)