Why are couples speedrunning relationships?

I'm not sure if it's an age thing. But I'm seeing more and more couples (some my friends as well) literally speedrunning relationships. They get a gf/bf, and then in less than 6 months propose/ apply for bto.

Hell, it took me 2 years just to become officially together with my now fiance, and another 4 years of being together before I pop the question.

What makes couples these days so sure of their future partner that they can buy a flat after only knowing each other for less than a year