May fought Cotto and DLH @154 because he said he likes fighting fighters at their best but he will not fight Canelo @154. I also don't think Marquez was @ his best when Mayweather fought him. IMO Mayweather is a great fighter but the only reason he's undefeated is because he doesn't take any risks. If you fight the best on even terms you will eventually loose.
Big difference, May wanted DLH's crown and spotlight, May also called out DLH that's why he fought on DLH's terms and conditions. Also Cotto never called out May, May wanted Cotto's title and he chose to fight Cotto because options were limited. Now Canelo has called out may, the P4P, payper view king, and cash cow. When you do that, you fight on that fighter's terms. Example Dawson vs Ward, Hatton vs May, Marquez vs May, Mosley vs May, Hagler vs Hearns. I can keep going, it has always been like this, led by Sugar Ray Leanord, Heck Ali when he was known as Cassius, had to give in the Sonny Liston's terms in the 1st fight, one of those request was a very small ring. Hagler even though he was the middle weight champ, had to give into Ray Leonard's terms, because Ray was the star. The ring was big as heck, the gloves were chosen by ray too. Bhop vs Tito, Bhop was the middle champ, but Tito was the star, Tito once again chose a smaller ring, and also got the bigger purse. DLH vs Pac, DLH called out and went down to 147, something he hasn't done @ that time in over 10yrs. Point is Canelo called out May, so why does May have to give into him, when May has clearly stated recently he's not comfortable @ 154, it's evident in both his fights vs DLH & Cotto.