Why?

Because it leads to way too much unfocused effort and time wasting.

You’re going to waste your time learning how to set meetings and talk to receptionists.

I don’t mean to malign receptionists, they are great people and the world needs them.

But you have an assistant who is going to do that stuff. What your company needs from you is to sell things and to make investors happy. “I need business English” is way too broad a phrase for either of those, and you’re going to waste hours and hours and weeks and weeks and all you’ll have to show for it is that you’ll be able to do low-value activities. You won’t be equipped to do what your company needs from you.

So be more specific:
“I need English so I can sell these blue curtains to those French customers.”
“I need English so I can sell my company’s software in Europe.”
“I need English so I can tap into the investor pool in London.”

I’m a native English speaker, have been all my life. But I’m still learning English. Sure, I might be at a higher level, but I’m still learning English.

And I’m happy to descend into this endless rabbit hole, because, well, I just am. But that’s just what it is, an endless rabbit hole. I’ll never reach the end of it.

You don’t want to wake up 20 years from now and realize 80% of your time was spent learning stuff you never used, do you? Your company needs you to sell stuff NOW, your company needs you to get that investment NOW. And you want to do those things and still make it to your kid’s piano recital, or home for dinner at a reasonable hour.

So don’t use that phrase, “I need business English.” Tell us what you want to do with it.