A single pastor in his 30's, assuming he's a heterosexual male who just hasn't found the right partner yet, would still be a wild card in a typical Protestant congregation filled with married women not all of whom may be entirely happy in their marriages, and the usual corps of high school age daughters still attending church as they haven't yet gone off to college.
The men in the congregation, including the ones serving on the governing board whose wives really run the place, are the fathers and husbands who might well prefer an attached and (figuratively) neutered pastor over one who might turn out to be a rooster in the hen house. Hence the safe choice, irrespective of any suspicions about sexual orientation, would be a married man.
Plus, the pastor's wife is usually expected to help provide the social glue that binds the pastor to his congregation. It's sort of hiring a team. One single man, without a supporting partner, may not be able to perform all the various duties expected of a full time minister as well as one with.
It seems like we’re presupposing a church model where one man is the boss and all eyes are on him, rather than a ministry team of people from different walks of life.
I think you HAVE to be married to be an Orthodox Rabbi. I don’t know about any requirement that he has kids, though I think that is expected.
That's a sad but possibly accurate statement. My daughter attended church regularly all through college.