Finding someone who works in the same professional field as you do can often provide fertile ground in which romance can blossom. No one understands the mind of a lawyer better than another lawyer, for example. Perhaps your career demands so much of your time that you cannot imagine having a partner who doesn't share your professional committments.
There's a lot to said for finding someone who has followed the same career path and who therefore works the same hours and who works in the same spheres of employment.