The way I think about this is:

You already are in "debt" by being alive. You have the huge liabilities of needing food and housing and maybe sometimes some healthcare, in order to stay alive.

By buying a perpetual source of one of those you aren't investing or expanding your liabilities-- just the opposite, you are hedging against and closing out your liability by prepaying for it. To take this idea further, this is why I think buying a little bit of stock in energy and agriculture companies is "risk free" because while they could go down if those things get cheaper, you would then win out as a consumer. You will need food and energy down the line anyway, so a modest investment in those closes out that hedge rather than expanding liability