I believe this stems from an issue with the steemit platform itself - visibility is crucial so being early on the stage is important. Often, this will lead to people making generic comments and not looking at the content. As such, typical comments on any post will just say 'Thanks'. There's nothing inherently wrong with this but it provides little to any discussion and is also made redundant because an upvote delivers the same message.

As the system matures further, I'm sure this will stop being an issue.