I'm curious if you have numbers on that or you are just assuming low yields.

I happen to know exactly how much a tomato plant grows because over 20 years of commercial farming I kept records. It varies a lot by variety and season and even how we are responding to market needs but in general I tend to get about 800-1400 lbs per 200 ft row for indeterminate tomatoes over the season. A farmer I know at lower elevation gets a lot more but they have a longer season, better soil and, crucially, water a lot more than we do -- my method cuts yield but increases quality. We use a 2 ft spacing for F1 varieties so that's about 100 plants (more like 95, but whatevs) so let's call it 8 pounds per plant = 48 lbs of tomatoes. Again, this is quite generalized and it's often way more. I also happen to know that's going to be on the very low end of home garden yields because people tell me this shit. Also, for cherry tomatoes you can get probably 60-70% more since they are very prolific.

Two tomato plants far exceeded what we needed. We sacrificed the remainder to the possums and birds.

They might just be in a better climate than you! I had far more delicious sun-ripened tomatoes over the summer than I could eat. More than six plants to be fair, but most self-seeded anyway.

exactly.

i've been gardening for years. it's a supplement. for like 1-2months i get nice produce that can feed a few people for a few weeks. but that's it. i maybe produce 20lbs of produce in a year if i'm lucky. that's over a dozen or two plants. i have a good sized garden of about 100 sq ft.

not to mention the weather any year could totally f you. one year we had three months of drought, so i got like 2lbs of tomatoes that year.

turns out i still buy like 95% of my produce from the grocery store... because it's available year round and it's hard to grow variety well unless you have multiple beds with differing soil and sun conditions.

most folks grow tomoatoes and cukes because they are easy and produce abundantly. but i am not going to live on tomatoes and cukes 365 days a year.

the space needed to grow squashes, berries, etc. is way way higher. you need a lot of land. and they are very low yield. a ten foot watermelon vine produces like maybe 1-2 melons per year and takes up 20 sq ft of garden space. a squash vine might produce 4-6 decent squash, etc. and a lot of veggies and plants are non complimentary, meaning they choke each other out if grown in proximity.

the only person i know who has a varied and big garden is an engineer who has spend five figures producing dozens of beds, water systems, and etc. and he still gets a shitty yield some years due to weather and he struggles constantly with rabbits, groundhogs stealing his crop. he has a whole trap and kill system for them even now. because the critters know he is the place to go for the tasty plants. most home gardening grow a few tomato plants and make some tomato sauce and throw a dinner party and that's the extent of their home gardening.

it's way more complex and difficult than some 'hrr drr just bring back victory gardens' nonsense. you're average person isn't going to be building a 1000sq ft veggie garden with fencing and dealing with all the part time job of labor and upkeep that it requires.