Just because Eric did a lot for Ariel, and Charming didn't anything for Cinderella, imo.

^Well, he got her away from her abusive family for one...

Smith starts out as a possesor with a superiority complex and a number of prejudices (directed at Native Americans that he perceived as "savages" merely because they were different from him and his people's standards of living) which is something that definitely wouldn't sit well with Ariel whose primary goal is to challenge prejudices like she did with her father's judgement towards the human world, however, she lacks the skills to effectively and operatively prove her point to an individual who sticks to prejudices which is why her relationship with Smith probably wouldn't start off smoothly. In addition to that he generally doesn't seem like her type at all. Smith isn't the sweet, charming, music loving guy that Ariel needs, he is way too problematic and Ariel isn't exactly suited to be dealing with problematic issues.

I don't see it at all, they don't seem to be each other's type.

Least happy-go-lucky, and I don't think he'd fit her definition of "handsome" either.

Definitely not but Adam heck ya