To Arthur, Sam Daily is a country bumpkin—so it makes sense that he's introduced as a "big man, with a beefy face and huge raw-looking hands, well enough spoken" (3.13). Notice that "well enough"? Arthur isn't about to admit that anything in this forsaken place is "good": it's just good enough.
But good or just good enough, Sam is friendly. Even though Arthur first dismisses him as just another country bumpkin, Sam becomes Arthur's greatest ally in the story. He's loyal and keeps an eye out for Arthur even when Arthur is unaware that he needs watching over. He even gives up his little dog.
"Take her," he said, "bring her back to me when you are done."
"Will she come with me?"
"She'll do what I tell her." (8.48-50)
(Literary analysis pro tip: if someone has a nice, friendly dog, that's almost always—we'd say 98% of the time—a clue that they're a good person. We can't vouch for real life working that way, unfortunately.)
He doesn't try to change Arthur's plans; he doesn't throw a fit and tell him that he can't go back to Eel Marsh House at all. He doesn't even tell him about the whole story of Jennet Humfrye at first. But he does have a keen eye on Arthur and tries to do whatever he can for him. When Arthur is at his lowest, he appears like a big, red savior:
I found myself lying, propped up on the couch in the morning room, with the large, red, concerned face of Mr. Samuel Daily looming over me. In his hand he held a pocket torch, with which, I realized, he must have been peering into my eyes, in a crude attempt to arouse me. (11.2)
In a village full of suspicious, closed-mouth locals, Sam is definitely Arthur's lifeline. And we bet he's pretty popular down at the local pub, too.