These periphrastic† (how's *that for a word) verbs don't always make a whole lot of sense but are often more widespread than one might think. For example the future in to go, as in, 'I'm going to explain in a footnote what I meant by periphrastic' is common enough in English and also in the Romance languages. The same is true of using have got or just have to indicate compulsion. Spanish uses tener in the same sense.

†Periphrasis is the use of a bunch of words rather than a single inflected word. Again in Spanish one could say voy a dejar, 'I'm going to quit' instead of dejaré (1st person singular future of dejar, to quit).