The difference is that real estate isn't just a financial asset. It's an exclusive claim on a sizable chunk of immobile physical space that potentially has many other uses, none of which can happen when it's full of whatever's there right now. This isn't true of a bond or a painting.

It's in the general interest of society to ensure that land is economically productive because it's central to a great many other aspects of life. This is generally intended to be reasonably in line with what its potential is. This also really isn't true of a bond or painting.

My answer is that real estate wealth is qualitatively different in ways both important and relevant from other forms of wealth.