I've found a lot more roleplaying in Pathfinder than D&D 3.5, but less in both than I do in games like SR, 7th Sea, Deadlands, etc.
I feel there are several contributing factors, but here are a few I'll list:
A.) Less Roleplaying reward. Use SR Mission as an example. In Season 2 most runs were giving 2-4 karma with another one to three for good roleplaying. That's have again in game experience for roleplaying. In a strictly time based sense, its worth going that extra mile for the reward (especially since its harder to botch the roleplaying portion of a run

). Now arguably Roleplaying is the entire point of the game, but a lot of people play RPGs like the do the video game versions these days, and if they haven't been exposed to a group of actual RPers they play a calculated what gives me the most style of game.
B.) Levels and Classes. The entire concept of levels and classes in the sense that D&D and D&D Clone (I mean Pathfinder of course) uses them shatters the veil of the world for a lot of players. Spending weeks crafting a sword only to, on a two day expedition, kill a goblin and suddenly get better at blacksmithing is just quirky. So is being forced to pick and choose your abilities in tidy little bundles. What if I really do want to play Jellian Lee Floustan, writer adventurer, why should I have to gain points in attack. Add in the fact that most pre-written adventurers and the guidelines for creating encounters are so stacked towards halfway optimized characters, there isn't near as much room for flavor as there is in classless and leveless games.
C.) World. Look through the core book for Pathfinder and D&D 3.5. Compare what it says of the world to games like SR, Deadlands, and 7th Sea. There is no comparison. Ya, its supposed to be usable in any fantasy setting, but it gives you such little information for a base setting that its hard to develop your character more than I'm Gary the fighter, I come from uhm...are there mountains in GM 128's world? Most other games have so much submersion into the setting that you're dripping wet when you're done reading the intro (before you ever get to character creation).
D.) Character Creation. Most games put an emphasis on what do you want your character to be and give examples (fast talking elf, sly and stealthy ork assassin, etc.) and suggest you know before you start building a character. D&D 3.5 and Pathfinder technically said something similar, but the examples they gave were always how do you want to fight rather than who are you (toe-to toe, mystical mage, stealthy ranged rogue). Ninety percent of D&D's creation seemed based on how you would perform in the inevitable dozen combats per level that crop up.
None of this is meant to say that you can't roleplay in D&D or Pathfinder, but that it is insanely easier to
learn to roleplay in other systems while D&D and Pathfinder are very good at teaching how to rollplay due to their extremely structured nature. Some of my critique may be a little harsh (I don't dislike either game particularly, I just am not fond of levels or classes at all. My first game was West End Games Star Wars followed closely by 2nd Edition Shadowrun, and D&D always felt more like playing a video game to me than any other RPG (excluding that horrible horrible game called
World of Synni...no it's too horrible I can't finish it)).
I remember sitting down to run Living Greyhawk for a group of players back in the day (they had been playing a while too, they were level 12 which at the time was quite a feat to reach in LG as most players didn't live past the entry slaughterhouses....errr...I mean modules) and having them look at me dumbfounded as I roleplayed the NPCs. It took me twenty minutes to find the tiny little section in the third edition players guide on roleplaying to let them understand what roleplaying actually was.