AEs doing their own prospecting

This is probably SaaS-specific. [Edit: also, I'm talking purely outbound].

My background is in product development and operations, not sales, but I'm currently in charge of building pipeline at a startup with $3M ARR, until we find a CRO type person.

I'm super curious about something.

Im recently hearing more and more that the days of the SDR role are numbered and that it's all about "full-stack" AEs who should be self sourcing deals and prospecting. I don't understand this sentiment. Prospecting/outreach and closing seem like very different skillsets to me, and it makes more sense (to me) to have people who specialize in one or another. Just like I have developers who specialize in either front end or backend software, yes there are full-stack developers but generally at a certain scale they end up mostly doing one or the other.

Why do people say that AEs have to prospect and do cold outreach when there are perfectly good SDRs to do that for them, and they can spend time strategizing and closing?

Update: deal sizes for us are in mid 6 figures per year, margins in the low 6 figures.