Tony can't recruite Daredevil

1. Daredevil's powers don't register in the public eye -- unlike strength and speed, having super-senses shows no visible evidence. Nobody but Claire or the Defenders even knows he's en enhanced human. To the world he'd be a normal vigilante so he has no real business in the Sakovia Accords drama.

2. Daredevil's powers are too limited -- At best, he can use his super-hearing to locate Ant Man. He'd probably beat Hawkeye and dodge his arrows pretty easily. He can't kick giant Ant Man in the face or lift an aero bridge though. If he tried to take the punishment Spider-man took he'd most certainly be dead. Past Hawkeye or Ant Man pretty much anyone else would have kicked Matt's face in.

3. He wouldn't side with Tony anyways -- Daredevil is literally the only super-hero with a secret identity in the MCU, aside from Spider-man. He obviously thinks super-heroes should do what they deem necessary to make the world a better place. If he sided with Tony he'd be a gigantic hypocrite.

4. He has no reason to care -- The Sakovia Accords deals with international rights and Daredevil only cares about Hell's Kitchen. Idealogically it makes no sense for him to want to get involved.

5. He's a grown man -- Tony recruited Spider-man because he's a teenage kld. You'de be hard pressed to find someone Matt's age to be as impressionable.