Alright, let's run a quick model.

Let's say the upper cap is $1000k.

You are a CEO and you get a salary of, say, $10k, plus 1000 shares, each worth $1. So, in total, that year your worth is $120k + $1000 = $121k.

Now, you're incredibly successful as a CEO, you make your shareholders drool for your company's shares. Which makes their price skyrocket. Each share is now worth $1000! Such success!

But wait! No! Catastrophe!

Your worth has just gone up to $120k + $1000k! The share's value on their own hits the upper limit of wealth!

They're not your money, mind you, you can't do anything with them unless you cash them in, sell them.

So, you have two choices - you stop getting any salary and have $0 for spending (hopefully the office cafeteria is well stocked!), or you sell some shares, give the money to charity, and pray the stock price doesn't go up. And if it does, you have to sell again, lose the money, and... oh, but now you no longer hold a controlling interest in your own company - some three dudes who work together bought up the shares, spread them around evenly (so neither of them goes above the $1000k), and they effectively control your own company, telling you what to do with it.

Companies shouldn’t be able to have over, say 1000 employees either.

So, instead of having some large companies, you end up with chains of "totally not the same" companies that just work together. "Oh, we've outsourced our HR to company X, which is Totally Not The Same as our company, they just don't work with anybody else and we have full data transparency with them."