Most of the spending of the middle class, and all of the spending of the working class, is already spoken for.
If you want to make money from the middle class, you have to do better at something than whoever is doing it now.
If you want to make money from the rich, you just have to dream up some new twist on their wants (sure, it has to be executed reasonably well, but you're not competing in the same way).
So sure, most of the money that changes hands does so via the daily/weekly/monthly spending of regular people. But that's not where the big money is unless you come up with a truly mass market new thing. The big money is in providing for the wants of the rich, because the marginal utility of what they spend on wants is so low to them.
Or you make what the middle class spends money on. This is generally an easier path. Making something unique can make money, but generally it is safe to assume if nobody else is making it, it is because nobody wants it -not that you are the first with a new idea.
If the middle class spends money on it, then in general, someone is already making it, has established customers, distributors etc. This is a high barrier to entry.
For what it's worth, I (mostly) disagree with your detractors in the other comments and agree with your sentiment (I think).
Markets care about "aggregate
demand". Rich people can be lucrative individual customers because they have more to spend and often less price sensitivity. But they have limited capacity for consumption in many areas; they only eat three meals a day and only fill so many airline seats at once. The middle class and even lower classes have much higher capacity for consumption and are worth targeting - think McDonald's or even Google (advertisers want all the eyeballs they can get, even if they prefer wealthy ones)
Wealth (i.e. net worth) isn’t the relevant statistic for how much the market “cares” about a particular demographic. Aggregate disposable income is.
A young doctor with $100k in med school loan debt is part of that “bottom 50%” of wealth but nonetheless an extremely attractive target for “the market”.
By default, company executives are beholden to the shareholders (i.e. the wealthy).
In a healthy competitive market, they're also reactive to customer desires, but when they're presented with the opportunity to decrease competition through consolidation or other means, it's blatantly obvious where their true loyalties lie.
