Why don't the Venu models have an integrated pacepro function?

I don't have an answer for you but maybe look around connect IQ. There might be an app or widget that address your problem for the time being.

PacePro is only for the FR series, Fenix/Epix, Instinct, etc. Garmin has to segregate some of the features for the advanced models. There is no idea if Venu 3 will get the PacePro function via an update in the future. We can just hope, but it is not guaranteed.

I'm sorry to say this, but the Forerunner 55 for example is not a high end model like the Epix or fenix and the pacepro feature is included in the Forerunner 55. The Vivo models are more premium and the pacepro feature is not included. And that's kind of weird.

I agree with that point. FR 55 is not a high-end model, but nevertheless, it's an FR product and not a Vivo or any other product. But the FR 55 misses other crucial metrics like Running Dynamics (which in my view is highly important and most basic for anyone focused on improving their running). PacePro is more like advanced running and maybe that is why Venu 3 doesn't have it. I am sad too, that Venu 3 doesn't have it, but more than PacePro, Courses is the main missing feature for Venu 3 in my opinion. Let's hope Garmin tries to bring something more interesting to the Venu 3. 

Edit: You can suggest ideas to Garmin and they might listen. Can't guarantee it, but worth giving a try.

www.garmin.com/.../