As Brother David says, this is quite a well-known phenomenon. Without wishing to generalise, I have heard of several cases where (after the fact, unfortunately) the individual concedes that they were in conflict about taking solemn vows or being ordained, but wanted to do the right thing, or didn’t want to let people down, as they saw it. Consequently they proceeded with vows or ordination in the hope/belief that this would resolve any doubts or fears that they had, but of course that doesn’t necessarily follow. It goes without saying that the formators and superiors of these individuals share some responsibility for not intuiting that the people in their charge were struggling, although they are only human and often have to proceed on what they are told by the candidate themselves.
I think this highlights several problems - firstly, that if you are an unhappy novice and an unhappy student you are unlikely to be happier simply because you take solemn vows. Secondly, that the ontological change associated with priestly ordination does not include emotional reconfiguration. And thirdly, that romantic notions of what consecrated life or priesthood are will not sustain you alone - it is possible to become bored or troubled within religious life just as one can become bored or troubled within any other situation, and something very solid must be present to help you keep going rather than walk away.
And that brings us back to the subject of the thread. As I’ve said elsewhere, I wear the habit, and I believe in its value. But there are lots of reasons why people don’t always wear religious garb, as Brother JR has clearly articulated. My fear is that anyone who enters a particular religious institute simply because of the externals will quickly find that clothing - the desire to wear which can be as much about feeling good about oneself as about orthodoxy - is not enough.
Perhaps some of the people who joined habited communities but left - and as stated above, the retention of people therein is not always particularly high - did so because they were too concerned about the superficial and had not sufficiently discerned the deeper implications of a vocation to consecrated life. Or perhaps they believed, as do some of the posters here on CAF, that simply putting on a habit would transform them into someone different - holier, happier, more fulfilled. If only it was that simple.