Because both India and China have been trying for a long long time to make it easier to get their citizens into this country. Irrespective of what people will think, both of these countries will be in a very strong position when negotiating a trade deal with the UK - we will be desperate for deals and for immigrants to work.
There’s nowt wrong with immigration, but for those who voted leave because of immigration are in for a rude awakening.
Edit - this post was meant to quote the why immigration with trade post.