As to the OP, snails can be a bit unsightly, especially many, many tiny ones. However, they do somewhat serve a housekeeping function. Some tend to have a somewhat short life span (in my tank anyway) so having shells left behind is just part of what happens. Mine were hitchhikers with floating plants. For the most part, I just tolerate them.Is that bad, well it all depends on your preference. Alot of people like them due to their burrowing nature in soil and sand substrate tanks. Some like them for part of the clean up crew. Some like them for the complete eco system which is the best of both worlds.
Me personally, I don't like the look of small snails. Mainly speaking of ramshorn and MTS. Nerite, Mystery and Apple, just to name a few, don't populate like roaches. Its very unattractive to see if they get out of hand. I can't house any in my tank due to my water parameters though. I use R/O water in which strips the water of what snails need to survive.