De La Hoya spent most of his time in the corner and on the ropes, was weight drained and throwing one shot at a time, thats why. Mosley wouldnt spend most of time on the ropes, he wouldn't be weight drained and I think we would see the Mosley who fought Magarito in against Pacquiao if they ever fought.
Oscar spent most of the fight following Pac round the ring! It wasn't until he started getting his arse handed to him that he backed up onto the ropes. You are essentially comparing Pac to Margarito, which is just absurd! Marg walks forward in straight lines, absorbing shots on the way in just to wail away with his own. He basically relies on his chin to get him into position to land his punches.
The only comparison I am making between the two is they are both easier to hit than Mayweather which they are.
Judging by how Floyd knocked Mosley around, it's clear his punch resistance is waning, despite the obvious speed and accuracy of the shots. PAC would've knocked Shane out IMO, in a more competitive fight than Shanes with Floyd, due to the different styles.
Or maybe Floyd hits harder than you think. Just because he usually chooses to box rather than brawl doesnt mean he has no power. As Nazeem Richardson said, 'I reckon Floyd is capable of turning into a dragon and spitting balls of fire' If Marquez had the power to stun pac you can be sure Floyd will. Lets not forget pac flooring JMM was always his mission from the first bell to the last but when Floyd floored him it was done intentionally to punish him for actually landing a clean shot, watch the fights again with an open mind