Lip trills

What is the point of lip trills and why are the used so much in vocal training? I mean what do they really help with? And exactly how important are they in vocal training really? Would it be a big deal if I just skipped them all together?? 

My understanding is that they're for training even breathing. The mechanics of the trill are such that if your breathing is uneven the trill will fail, so it's just a really good way to train constant even breathing. I'm sure there are other ways to train this, maybe someone will pop in with an alternative.

Personally I found the trill really really difficult at first but it eventually came to me. Try putting your thumb and first finger tips on either side of your mouth as if to shorten the width of your mouth, this helps a bit. There's a great demo of this in one of the first few videos of Jonathan Estabrooks' beginner course, but I forget which one. 

A singing teacher* gave me the okay to roll Rs instead of lip trills as I couldn't manage them, even with the thumb and finger trick. I don't know if this is a full alternative; maybe there are aspects of the trill that are lost via the rolling r. But since that teacher said it would basically do the same thing, I've just switched to it entirely.

*outside of 30 Day Singer, part of a physical and certified music school in my city.

Edit: there's a post in this forum further down in which a commenter responded with a link to a 30-Day Singer video on lip trill alternatives.

Lip trills are an SOVT, the benefits of which you can read about here: https://www.voicescienceworks.org/sovt-exercises.html. Why lip trill instead of another SOVT? I personally like how easy it is to assess airflow and work on consistency of airflow with the trill. I find them relaxing, but if you struggle with them and they're causing frustration or tension, please substitute with another SOVT from that article! I'm including more links below from another forum thread. 

Straw singing is a great replacement for lip trills! Here's a lesson on other lip trill alternatives too: https://www.youtube.com/watch?v=0wzbyyl1d-I.

Here's an article on lip trills and a short lesson with extra tips as well!