Working remotely from another country is easy. Paying somebody in another country is not easy at all. Even with specialized providers it is a substantial hassle. Without it you pretty much better give up - the chances you get all the payments, taxes and paperwork right is minimal, and that country's tax/regulatory authorities would be more than happy to fine you and/or your workers if you don't. In the best case, in worse case they might just seize your money intended for payroll and keep it until you figure things out.
(I know it's not quite that simple, but I think it's interesting to think about.)
One you exchange the money - where an advantage can be gained - then it can be considered a sale and thus taxed. A sale does not necessarily need to be towards consumption.
But, if such a system was in place, the money would be taxed during the purchase of the investment vehicle. A sale is a sale. Unless the money is literally stuck in a mattress, it is going to be taxed upon doing anything useful with it. If it is simply stuck in a mattress for all of eternity, one is really no further ahead. Money only has value when you can use it to facilitate a sale; and when there is a sale there would be a tax.
In point of fact, the US mortgage interest deduction is highly regressive. It favors those who can afford a down payment on a house over those who can't, who by definition will be poorer.
If the sales tax applied to buying a house, it would be quite progressive. It could even only apply to the cost of the house less some amount (say, $100k) which would make it even more progressive.