As sour_grapes points out, these kits generally come out of Canada and they were developed because there was a market for them. Our alcoholic drinks are very expensive to buy here because they are taxed so high. There is a fundamental difference between the European view of wine/beer consumption from that of North America. Yours is that of an inclusive part of your diet; ours is that of one of the root causes of all evil. We cannot legally consume alcohol until we are, usually, 19 or 21 and its use is very tightly controlled. Alcohol, along with tobacco products, are prime candidates for "sin" taxes and it is very easy for governments to increase taxes on these. Thus our alcoholic beverages are very expensive.
Wine kits have been available for many years but in the past 10-15 years have become more and more popular as more people switch to wine drinking. The kit quality early on was not good but now many kits, and certainly the ultra premium kits, produce a top quality product, better than the $10-15 wine I can buy.
So economics is what started it and continues to drive it here in Canada. But it is more than that now. Wine drinkers are much more mainstream now and they want access to better and different kinds of wine. Kits manufacturers have recognized this and are trying to meet this demand, by sourcing their grapes from better vineyards around the world. We are able to make wines from grapes normally not available to us and in blends unavailable to us and we can do this year round without special equipment. We can buy a great kit on sale and make it at our leisure instead of needing to make a juice bucket or crushing grapes immediately or keeping it frozen until we do. Even getting fresh grapes or must where I live is extremely expensive (shipping costs in Canada are very high) and I suspect it is similar in many other areas.
Then there is the DIY aspect you have mentioned. There is definitely a satisfaction factor involved, whether you make your wine from kits or grapes or juice or fruit. These processes challenge the home winemaker to make a better product and it can be very self-satisfying. Combine this with inviting family and friends to help with crushing/bottling/drinking and it can be a great social event as well.
Kit wines have proven to be popular and viable in our part of the world but somehow I just don't see that happening in your area. I don't think your wants and needs would support this.
I hope this somewhat answers your question.