Yes, what Andy said.
Mise en place is critical in wok cooking because these recipes can have a dozen or more ingredients that require chopping or mincing or some sort of cleaning e.g. shrimp/squid. I have literally spent 2 hours preparing to cook a Thai or Chinese dish, and then the final cooking takes 10 minutes. (That's why I used to have that phrase in my signature. I knew that other Asian cuisine enthusiasts would realize my sig was about Asian cooking.)
If you didn't have the ingredients all ready to go, you would have to stop in the middle of cooking and that would ruin the dish.
A second reason for doing that is that it's very time consuming to do all that cutting and chopping. I don't mind it because I find that kind of work meditative, and because I'm a perfectionist and I like to get my ingredients all exactly right.
Particularly when I'm entertaining company, if I don't do preparation in advance they're in for a very boring time watching me slice and dice, I'll be distracted from giving them my full attention, and I won't enjoy my company as much because I'll be preoccupied with food preparation--or worse, I'll get the preparation wrong and the dish won't come out the way I want.
It's not unusual for my guests to tell me, "This is sort of like watching a cooking TV program."
That's nice, everybody can be a star in their own kitchen. And of course this is why you often see TV chefs using the same technique. Otherwise their show would be long and boring, and it's assumed that the audience can already chop and measure, or can learn it as necessary on their own time.
When I'm cooking for myself I sometimes just push ingredients to one side of my cutting board, assembling a communal pile there, since of course they're all going the same place.
I just did a census and I have over 30 in about 5-6 designs/sizes. I have probably more than I intended because I thought I had some in storage so I was buying more to be able to
mise en place in my temporary residence. It's still possible I have yet more in storage. In any case the dishes are glass so they suffer a low but steady mortality rate (oops! smash!) so I buy more occasionally just to keep up. One of the little 79 cent dishes I bought last week already went to dish heaven.