A tax certificate explains that you have paid taxes somewhere on your money. Sure it︀ doesn't mean that the money comes from legitimate business but it clarifies the fact that︁ you have paid taxes on that money, even if taxes are 0 like in Dubai.︂
The issue is not only with your home country, in whatever country you go, at︃ least in Europe, and buy a house, you will get asked from where that money︄ comes from and if you have paid taxes on it. You can't go to Spain︅ and buy a house and say to the hacienda that you have no tax certificate.︆ That's what I mean with "you can't use your UAE money", if you stay in︇ the UAE less than 180 days and get a tax certificate, which is what most︈ digital nomads do.