I think they get called up for International duties midst of almost every IPL season. Hence a bad choice to put too much money on English players if you're going to lose them just like that after having built momentum with those players. If not, good; at least you get to test rest of your squad. Maybe that's why IPL franchises have been neglecting many good English players over the years; Joe Root to start with. Unfortunately, RR owns two biggies of them.