Earlier quoted context omitted.
A once-weekly subcutaneous injection is not a big deal for most people I think, outside of those who are very afraid of needles. It's a tiny needle and you don't even feel it. I've given injections to people who are afraid of needles, and they sometimes close their eyes in fear and are begging me to "just get it over with" without even realizing that I'm already done. Anyway, all this to say that outside of needle-ph…
As someone who is mildly needle-phobic, I'll agree it's no big deal, but you definitely can feel it, and if you hit a blood vessel by accident, there's a (mostly painless) bump and 2-3 week bruise at the injection site, which might be a major issue for some.
You do not want the drug meant to subcutaneous to go into the blood steam. This is true for GPL-1s (all peptides for that matter), as well as insulin, and definitely mRNA vaccines.