A couple of thoughts.

If you've been using the shoots for cooking, you have been taking away leaves necessary for good growth for the onion plants. A little nip here and there is not a huge deal, but an onion only has so much to it, and needs most of its leaves for photosynthesis.

Onions usually bulb while they are still very lush. If they look tired, and haven't bulbed at all, it may not happen.

Onions are a biennial. This means they grow and bulb the first year, then die down. After re-sprouting the second season they flower and set seed.
When planting sets, you're actually planting second season onions. Depending on many factors (variety, timing, weather, light, etc) they sometimes skip the bulb and go straight to the flower. This may be what's happening with yours.

Next year if it doesn't work out, i'd try buying plants or starting you own from seed.
Good luck.

-Mark

Thanks for the reply. I haven't been snipping them a lot (they always have leaves), but maybe the weather it wasn't cool enough this season for them to bulb up. If they flower I will save the seeds for this fall and maybe the beneficial insects will love the flowers too.

Zach