There are lots of synthetic foods. The main problem is marketing. How are you going to sell your lab food when "processed" is bad and "natural" is good? The organic movement has taught people to distrust science in food, and its not something that is going to easily be reversed. The fact that most synthetic advances are used for cost reduction - not health doesn't help here either.
The only place where this has seen any adoption is synthetic meats. But I expect vegetable replacements to be many decades off - if ever.
For a real world example sugar was first synthesized in 1953 https://en.wikipedia.org/wiki/Sucrose#Chemical_synthesis
Carbohydrate synthesis is also a well studied field. https://en.wikipedia.org/wiki/Carbohydrate_synthesis
Many vitamin additives today are artifical. And of course artificial flavoring has vast commercial adoption. In the case of McDonald's french fries this was used to dramatically reduce the amount of saturated fat while maintaining the beef flavor - they are no longer deep fried in beef talow.
We can't yet recreate the texture of a pepper, but we can certainly create a synthetic smoothie with the necessities of life. Organic chemistry is a rich field of study.
Of course there are a few simple compounds which are edible, but most artificial additives are extracted and processed from grown inputs, and this is susceptible to unexpected health problems as happened with exposure to trans fats for decades - now banned.
> we can certainly create a synthetic smoothie with the necessities of life
That is a low bar - being capable at any cost to synthesis a smoothie with 'the necessities of life' including growth? good health? You didnt even reference that.
The food landscape is filled with pseudoscience, and whether a compound is synthesized or extracted is more of an economic decision not a scientific one.
Small amounts of almost anything can be synthesized at great expense, but you should have provided an example of a wholesome food which would not be completely uneconomical to synthesize (and purify) in bulk, to support a claim that there exists such a potential economic possibility. Even how much for example, it costs to synthesize food grade sugars would be a start on showing your advice on this subject is grounded in reality.
Food is more complicated than this picture. So much that nutritionists have major differences over which basic materials are beneficial in bulk and which cause health problems. Vitamins, minerals and medicines are not automatically absorbed well by our digestive system. The many biological foibles of human metabolism and our symbiotic gut flora, still confounds expectations about what food can be and can do to health.
There have been many, perhaps endless attempts to synthesize a wholesome food product - it would be worth a fortune. I am aware of zero successes to date and this shouldn't be the case if its not very difficult. We don't even synthesize sugar for consumption - maybe start there, but it is not even clear if/how much it causes diabetes or other diseases.
We might be stuck for a while longer with reliance on foods that needs to live for bit (plant or animal) before we can sustain our own lives with them - seems to be a very old system requirement of multicellular life, and one that has not been cracked yet.