[monob]

Because it destroys the local industry which you will need at some point.

As simple example: the British supported the German chemicals industry prior to WWI.

At the start of WWI, the money the British spent had been turned into German chemical expertise. This lead to the development of the Haber process, poison gas, and generally making Germany a powerhouse in chemicals in the same way Britain was in mechanical manufacturing.

If a tariff had been put in place on German imports to Britain the German chemical industry would have been much smaller, with much less capability and WWI would have finished in 6 months because Germany would have run out of nitric acid for their explosives.

[averagewall]

Are you saying it's better to keep underdeveloped countries technologically disadvantaged in case your own country worries they're becoming too powerful and so starts a war with them to keep them underdeveloped?

Another way to stop wars is to accept that somebody else is more economically productive and let the whole world benefit from that instead of trying to destroy it.

[monob]

That's a very naive way of looking at the world.

Economics is only allowed a free reign so long as it meets the goals of those currently in power in a given political unit.

Try selling nuclear technology to Iran if you don't think that it applies to the US as much as to China.

Doing it strategically to prevent a nuclear war 30 years down the line is the lesser of two evils.