Why developed countries want developing countries to liberalise their trade and investment?

Why developed countries want developing countries to liberalise their trade and investment? What do you think should the developing countries demand in return?

Developed countries want developing countries to
liberalise their trade and investment because the MNCs belonging to the developed countries can then set up their manufacturing centres in less expensive developing nations by investing there, thereby’lowering their manufacturing costs. This will increase their profits.
In my opinion, the developing countries should demand, in return, for some manner of protection of domestic producers against competition from imports from the developed countries which are subsidised by them.
Also, some additional charges should be levied on MNCs looking to set up base in developing nations.