I understand this because I can't get used to systemd. The learning curve should be better than rc.local for my taste.
Problem is systemd helps you booting fast and this is important both in the cloud (where every minute is a billed), and in telecom (where you have a stringent SLA to cover).
Why? When I used Arch Linux I did not ever turn off my laptop, but hibernate it. I only ever booted it when I stupidly forgot to plug it in before the battery runs out. And 10-20 seconds spend on a sequential boot every 10-20 days is just no time. We spend at least 100x that time in the toilet every day.
Problem is systemd helps you booting fast and this is important both in the cloud (where every minute is a billed), and in telecom (where you have a stringent SLA to cover).