Marriage gives people experiences which can not be got outside of a long-term relationship, and which enhance their ability to perform in the pastoral side fo the role of a priest. I am not talking about the sexual acts here, but about the experience of living with someone as an intimate partner, with all the ups and downs of any such relationship.
That said, there is nothing against this experience having been acquired and the relationship no longer being in existence, so yes, Ecu, a divorcee or widdow would also have this extra knowledge (though of course the RC tradition does not allow a divorce so in their eyes a divorcee is still married and inelligible for the priesthood!).
The other problem with an enforced celibacy is that it has been used as a cover for homosexuality. Men who were not geting married in the RC were frequently asked why not - and when homosexuality was a crime this was rather difficult - indeed it is still a bit difficult as it is seen as a sin to be this way by many (and even more see the act as a sin).  As a resuly, in order not to be asked this question a large number of gay men have gone into the priesthood, so they are no longer expected to be looking for a wife! The trouble is that it did not stop them from being attracted to othe men, and was a contributory cause of the scandal of priestly abuse of boys in the Catholic schools...