Frequency of usefulness is a large part of what determines a spell's power level.Frequency of usefulness isn't the metric; it's the power of what you can do with it.
If a given spell is so useful that it's being prepared and cast every day, that's a good sign the spell might be overpowered either in relation to other spells of its level or - in some cases - overall.
See, there's a difference in philosophy: I'd rather move the 5e version of CL up in level than move Tongues down. 5e is already IMO too easy, no need to make it easier yet.In my mind being able to communicate in a language, and potentially influence others, is vastly more potent than merely understanding it.
But I could see moving Tongues to 2nd level.