Why do people like Hank so much?

I think because he's just an honest, noble GOOD guy to the core. He almost ALWAYS tries to do the right thing.

Occasionally, I feel sad for the guy, his having grown up with Cotton as a father. I enjoy seeing the various ways his oppressive and abusive childhood manifests itself now that he's an adult. Plus I think a lot of us know people who are like him or similar in many ways.

Even though he thinks his son comes up with wild ideas, he always ends up supporting him. He also treats his wife and friends well for the most part as a faithful husband and loyal friend. He is a little stuck in the past, but he always seems to come around.
Dini

It's simple: Hank says what he means and means what he says. In a time where we EXPECT people to lie to us or let us down, if Hank says "I'll be there to help you at 5pm sharp" you know he will be there to help
Hank is a true blue Texan, like me. Born and bred where your word is EVERYTHING in a world where most people's word means next to nothing. A handshake is better than a signed contract. All this sounds cliche, but mention it to a 50-year old who was born and raised in Texas by Texans and they'll agree with it all, corny as it sounds

I love Hank. He's the voice of reason in the town of Arlen.

Fluttershy loves Discord

That's cuz Hank is real, he's genuine, he's true to himself.

Of course he's not perfect, but then again who is? I wouldn't be unhappy if he was my friend.

Cuz he's doin God's work, I tell you whut.

He is one of the few genuinely decent people on the show.
And, yeah, his son IS a freak. And Hank's a wise enough man to understand that Bobby's nonsense will not fly in the real world - and that his idiot kid needs a strong work ethic. He's not downright abusive like Marge and Homer Simpson, I'd say Peggy's far worse in that regard, he just knows the world and wants his son to do well.

And is he a bit stuck in his ways? Sure. But when he's confronted by bad people, intolerant and nasty sorts, he always stands his ground and sticks up for the little guy.

He's a fundamentally good person.

He gives good advice, and he always follows through and completes his promises.