There are probably fewer Engineers because they aren’t ‘the best’ at anything. They can fill just about any role needed and can provide great support. They are great at applying conditions as well. Perhaps they are just misunderstood, and therefore underrepresented.
I agree that with kits and few weapon selections the aesthetic quality of the engineer isn’t as high as it is with other professions, but that is what’s unique about them. They aren’t the flashiest, but sure are the quirkiest.
I love my engineer because I can change a couple utilities and have a totally different play style. I never get bored because of this. I have multiple sets of armor so I can be a support class, condition bomber, HGH might stacker, or burst SD build. I think if more people knew of the versatility the profession has more people would be willing to play them as their ‘main’.