To be honest I don't have my own child
No shit, Sherlock!
Fairly sure if another adult spoke to you the way that you speak to your children you would not like it. 'put your shoes on now' 'go to bed now' 'get in the car now' many other examples, or changing your tone of voice to be different than if you were speaking to another adult. Why do parents do this
You're correct, I would not like it. But also, another adult wouldn't have had to ask me 32 times to get ready to go out before I agreed to do it.
Yes, you should sometimes give your children choices - trainers or wellies? Pink or blue t-shirt? Carrots or peas? Fine. But shoes on now because we need to go to school? Get in the car because we need to pick up your brother? Go to bed because we need to get up early tomorrow? Go to the supermarket with me otherwise we won't eat tonight? These would be non-negotiable in my book, and no, I am not going to bribe my child with chocolate - all I've done then is teach my child that if I want them to do something, they can hold out for a bribe each and every time.
You should ask your child with respect. But equally, there will be very few parents who have not, as some point, told a child to 'do it now'. Some children, even after you have asked with respect, several times, just won't do it. If you are shouting often, then something clearly isn't working. But the occasional shout does no harm at all. I think it can be good for a child to understand that sometimes they've just pushed you too far.