Because the ALPA leadership isn't really hated by most pilots. It's just a few blowhards on the internet. When the ratification vote comes in tomorrow at Spirit with a wide margin, you'll see that what goes on on internet pilot forums has little to do with reality.

TAs ratified by wide margins at Hawaiian, Alaska, Jazz, and Capital Cargo in just the past year and a half. ALPA lobbying has led to a deal in Congress to raise pilot hiring requirements to 1500 hours, eliminating 200 hour pilots at the regionals. ALPA lobbying has also led to the flight time/duty time change proposal that will probably be issued soon by the FAA. Numerous smaller legislative and regulatory victories have also been achieved over the past year or so.