As the prices have dropped, the price difference between a 24" and a 32" TV are not so great and most people are just buying a larger TV because their wallet doesn't feel too much pain.
Thus, the market has largely shifted to larger screens and the marketability if odd-ball sizes like 26" and 37" TV's is pretty poor.
I don't know what determines which sizes become standard (24" certainly has become a standard) and which are odd-ball, but if you have a special nook for a TV and you need a 37" to fit, you are SOL.
The more common buyer, not having that restriction, would simply buy a 42" (or larger) to replace the 37"!
I have a friend who found a 43" TV to fit her entertainment center perfectly. She is lucky because (assuming she wants to keep the entertainment center forever - and it is a full wall of her house) the more standard 42" size still looks reasonable.