You expend labour; they build capital. The capital you build produces returns long into the future, but you don't own any of that future income stream. Sooner or later, your sharpness and skills will decline, and your labour will be relatively worthless. The capital you helped build will continue to be valuable (presuming you did a good job).
It's a poor deal if you're in a competitive market where there's another schmuck willing to do your job for just as cheap as you do it. But if you have pricing power, you'd be a complete fool not to either charge substantially more, or demand some ownership.
So you're okay with the fact that they are kinda-sorta exploiting you (by not including you as a co-patent holder) but have reservations on employees utilizing company resources to further their career?
That seems like a really raw deal to me. You might argue that you are "paid" to do this; not really, you can just coast on 9-5 and draw the same (or in the same ballpark) paycheck as someone who is busting his behind to invent something. Also when there is downsizing you might think that contributions is the only thing that matters, but it is demonstrably not (I'm speaking about regular companies not a small startup).
It's a poor deal if you're in a competitive market where there's another schmuck willing to do your job for just as cheap as you do it. But if you have pricing power, you'd be a complete fool not to either charge substantially more, or demand some ownership.