Nicky...some of us are totally obsessed with tomatoes! I started 19 varieties this year, and have had at least 6 varieties every year for the last 6 years, and never less than 2 any year I've grown them. A lot of it is to try different varieties for taste, or to see how well they do in a given climate, or a given year. In my case, it's all that, plus hoping to get plenty to sprout, and then survive to the fruiting stage and beyond. I tend to plant 6 seeds of each thing I'm growing, I generally have 4 to 6 seedlings, and always put at least 2 in the garden, in case one dies. This year, for instance, a neighbor's dog stepped on and dug up 3 or 4 plants that I had taken great care to get seeds for and grow out under lights indoors...if I hadn't had several of each, I would not get to see the results of all my hopes and efforts. I'll probably grow at the very least 40 plants this year, 60 if I can get enough spots prepared, and much of that is just so that I will have lots for my wife and myself. We have a very harsh and unpredictable environment here in central Oklahoma, and I've had near total failure, the year of the locust plague, in particular. In my case, though, also, I'm trying to becaome expert enough to begin selling plants, fruits and seeds someday as a profession...that's because I love tomatoes and tomato growing so much that I want to do what I most love as a profession. Try a few of the OP, (Open Pollenated aka Heirloom) tomatoes and see if you don't became a fanatic, as well! Even growing the hybrids from scratch is more rewarding than you could ever imagine!
Gee, I kind of got excited, didn't I?
Growing tomatoes consumes a lot of my life, I'll do it till the day I die!
I gave up most of the garden space I could have used for other crops this year so I could grow more tomatoes, and I consider it a successful growing season if I get even a few dozen "home growns" and nothing else from the garden!