Like many here, I totally and vehemently disagree with the fourth reason for rejection (the "n00b"): if someone has a proposal that is worthy of presentation, they should be given the opportunity to present -- regardless of their age or experience. There are many reasons for this, including the most obvious one that if every conference insists on experience, no one will be able to get that experience. But the reasons for not depending on prior presentations run much deeper: if you are going to evaluate a proposal based on the speaker's prior presentations, you are tautologically unblinded in your review process. Having an unblinded review process is a grievous mistake: when conferences aren't blind in their reviews, they end up confirming their own biases more than selecting the best possible work. (I have always felt this way, but my feelings on this were galvanized by my own experiences inside the sausage factory[1] -- and for the conference that I am currently organizing[2], we are emphatically double blind.)
I understand the problem of creating engaging presentations as well as compelling content, but there are ways to achieve this other than being prejudicial. For example, if you want to create an invited talk or two for those whose presentations the program committee particularly likes, great. And if you want to provide presentation coaching for those who you accept who haven't presented before, even better. (I have provided this coaching informally in the past, and have found that a little coaching can go a long way.) But a blinded review process must be viewed as a constraint on the problem: to do any less is to deprive ourselves of the new ideas and presenters that provide us our collective vitality!
[1] https://www.usenix.org/conference/atc16/technical-sessions/p...
[2] http://systemswe.love/