There is nothing wrong in using these words, as long as it does not sound artificial.
Moreover, there are various ways of saying Thank you, and it is important to understand these.
For instance, if we are sick in bed, and a relative not only comes calling, but also uses his influence with the doctors to arrange the best possible treatment, we should say " but for your help, all this would not have been possible". It is also wise to repeat this in another way, even congratulating the person for his resourcefulness. For instance, it may later be known that the Chief Doctor has a son, who is a student in the school in which our relative is a teacher. We could say, " it is nice to know that the Chief Doctor's son is your student?" and leave it at that. It is quite likely that our relative would say" yes, he is a very bright student'. This is exactly how the conversation goes on to strike positive notes at every step. The Thank you is part of the whole conversation but we are not overdoing it at all.
Similarly, when we use the word "Sorry", if we really mean it, and follow it up by doing something good the next time to the same person, (where we have long relationships with the other person, and his not a stranger with a one-off experience), the meaning of the word sorry would register in the mind of that person for a very long time to come.
More so, if we tend to forget the entire episode, and get on to only good things. For example, some mothers say "Sorry" for the violent behavior of their son or daughter, more specifically, if the child is just five years old. They then follow it up by reprimanding the child with the help of the father, and some sane counseling. This will seal the issue, as the son or daughter would have seen their mistake in the first place.
So, what matters is the wider context. The art of inter-personal relations is never complete without appropriate body language. People always look for honest responses. If the response is artificial and not sincere, they will easily see through the game. Such responses should never happen.