The idea is that you are limited in the number of turns (out of ctrl), so if it was just arrow keys, for example, every press would be counted. But by holding extra button, you can change and choose the direction without losing anything.
But I agree with you that in a lot of cases it seems redundant. So, I think to allow players to change the direction immediately with pressing just the IJKL/WASD, or they can still use ctrl+button.
Thank you for your opinion, though, it is highly appreciated! I will fix this, without a doubt. Thanks :)