Due to the humankind general evolution conditions and present cultures,
Girls provide sexuality (in a very broad sense, in terms of sexual attraction, stimulation and intercourse) and expect care, respect, .... and love.
Exchanging something so trivial (as they perceive it) at the price of most valuable things, including love....
Therefore they feel they are poor because they cannot afford such an (unfair) deal...looking for love at the expense of sexuality...
Then they are anxious because
they think (unconsciously)
they are avaricious, so that,
they want more than what
they have...
Of course, they possess love and other valued capacities....
but the the point is, nobody (no boy) wants (normally, in the FIRST STEP) those things from them...
Moreover, if they lose their current relationships (and loves), then they have to find and start such a cheap and unfair deal again...and again...
and this repetitive cycle makes them even more anxious ...
and more anxiety means more inner conflicts and more irrational, unreasonable and contradictory reactions...
From the other side, boys cannot understand why they have to exchange sexuality with care, respect, ....and love.
They know, somehow, the importance, but cannot figure out the exact relationship between those (i.e. sexuality and love) at first glance.... then they will be confused...
And after all, they will not be so convenient with such an exchange....they will think these are not really exchangeable at all....
Thus, a true love can be rare, and even if both sides can overcome these initial issues, it will be vulnerable, because always there is a possibility in which, the initial anxieties surface again....