Seems pretty obvious to me that the amount of contact with the opposite gender plays a huge part. Since most married couples are heterosexual and Engineering is still dominated by men, so contact of any kind is more rare.

On the other hand, dancers and choreographers are very likely to be dancing or choreographing with someone other than their spouse, at a very close physical distance to very fit partners who are nearly always the opposite gender. Jealousy and infidelity probably both play a part there. Same goes for bartenders -- the chances somebody comes to my engineering firm looking for a hot date? Not much, but a bar? That's a little more likely.

And lastly, I had to chuckle at agricultural engineers. All I can picture is a guy designing a combine, alone, in the middle of a cornfield. Good luck meeting someone ;-)