The onion variety I grow cannot be found at stores or the farmer's market, Alisa Craig. It is a large sweet onion that keeps fairly well. Over the years it has become my family's favorite and the only one we grow.

I think you'll find the same is true for onions as other vegies and fruit. You can grow varieties that you just can't find elsewhere, and the quality of what you grow will exceed what you can buy in most cases. Whether or not onions are worth it for you to grow or not is of course a personal decision...

I grow it for my canning needs - I am doing a lot of canning and by the time other produce is ready to can, onions are ready. I need about 1lb of onions for 3-4 lbs of produce, so free onions serve its purpose well)

Let's add in the convenience factor. When you have stored onions and shallots in the basement, there is one less thing to think about for several months.

If gardening were only about money, we would not be here.

But in terms of productivity, onions mature early enough in my climate to grow something else after them -- this year it was fall cabbage. This time advantage plus ease of storage plus interesting varieties make onions worth growing. Starting the seeds in winter keeps me off the streets, too.

I asked this question because I have an area to deer population. So I'm searching for the crops deer would not have interest at all.

Clearly onion is one of the few crops deer not interested in. I thought of pumpkins, but they are the least efficient crop to grow in terms of yield per unit area. Instead, onion is one of the most efficient crops to grow.

I like onion. I think I'll need to find the onion varieties that are easy to grow and also premium to the ones readily available in stores.

Lots of reasons. I grow then because they are super easy when using sets or transplants (both of which I can get for a very reasonable price at a local farm/feed store). Onions never have pest problems for me. No large animal damage either: never lost them to groundhogs, rabbits, or deer. They can wait a bit to be harvested if I'm on vacation for a week or busy with other things....unlike beans and zucchini which will shut down production for awhile if I neglect to harvest. I can grow as many as our family uses in only a small part of the garden. I can use them when they are young or wait til they mature. They are relatively quick and easy to harvest and are easy to store for a long time. I don't even have to can or freeze them to keep them for several months. I like being able to eat something from my garden as many days of the year as possible and softneck garlic and onions make that easy to do even if I don't do much freezing, canning, or drying. Sure, I could buy them for very little $, but they aren't "mine" and being "mine" makes them special to me :) So, yeah, lots of reasons!

If I had very limited space I might concentrate more on high $ value items and super tasty garden produce only. But for now, I'll continue to grow some onions each year.

BTW, deer around here LOVE pumpkins, but I've not had them bother onions.

Our deer enjoy the alliums quite a bit, and are even able to pick out our shallots from regular onions. They prefer the shallots, but when greens are in short supply, they will eat either. The damage is pretty dramatic: they usually bite the plant near the base. The cuts are about as good as scissors make. When they hit the chives, they trim out the new, tasty growth, and leave the older leaves.
Renais

I grow Onions because I can!

The best reason to grow onions is to get exactly the type and variety you want. I grow potato onions and Copras, because both keep from one harvest to the next and both cook very well.

OldDutch and NatureGirl pretty much summed up the majority of my reasons, but one additional reason for me is that commercial onions have sometimes been treated to make tops die down uniformly or to prevent sprouting, and I know my onions haven't been treated.