Sir you may be a joke but the Department of Jokes is nothing of the sort. Our integrity is not for sale.

The Romans colonized and settled Hispania and Gaul and Dacia, in large part because their wars of conquest there were also wars of annihilation and depopulation.

Such numbers are necessarily a rough estimate, but Gaul probably had a population of ~5 million before Roman conquest. Historians generally agree Caesar killed about a million, and enslaved another million or so. So it was a HUGE reduction in population.

The conquests in the east were nothing of the sort. Pompey basically just marched through and collected surrenders. The local populations were huge and urbanized, and the Latinate Roman population was never large. So while local elites might have learned Latin, the average person in the street never did.