Small players have so much more flexibility than a big boy. Systems are simpler, billing is a lot more manual when it comes to discounts/contracts/etc, and many only run a core network and get the tails else where (like from a big player).
Large companies don't have to be as slow to react as they sometimes are, and some ISP's are truly glacial (I'm looking at you Vodafone!). Until the middle of last year I worked for a multi-billion turnover company that regularly monitored it's main competitors and responded to their specials and price cuts within hours. Hours.. Not days.. not weeks, let alone the months wee sometimes see from ISP's. I know to a degree it's apples and oranges with different types of markets, but just being "big" doesn't preclude responsiveness or flexibility if the company has good systems and delegation in place.