Some of them are made to be flipped - I don't know if it works with all of them but some of them are made to be used as a high chair one way and a bucket holder the other way.
Reasons to leave the baby in the bucket - baby is sleeping... mom wants to eat a meal with hands/lap free (nothing wrong with this!!!)... mom doesn't like wearing baby... baby doesn't like being worn ... baby is happy where he/she is and picking him/her up is liable to start a cycle of cry/comfort/put down/cry/comfort/put down which doesn't go over well in a restaurant...
Baby wearing is not always mutually enjoyable for mom and baby, and having the baby in a car seat/carrier/bucket does not make an inferior parent. As long as everyone is happy and the baby isn't screaming and being ignored - hang the "experts."