I read romance and write romance. One of my pet-peeves is when the characters kiss way (!) before they deserve to. It makes everything about the relationship seem cheap, and more like lust than love. I'm not likely to read on. I know it's a personal bias. There has however a lot of info about building satisfying relationships between characters that explains why some readers will react this way when the physical relationship zooms ahead.
At first it's all about ATTRACTION
Step 1: Eye to Body you like what you see
Step 2: Eye to Eye eye contact
Then it's about BECOMING FRIENDS
Step 3: Voice to Voice getting to know each other, flirting
Step 4: Hand to Hand first touch
Step 5: Arm to shoulder getting closer
Step 6: Arm to Waist more intimate and personal
Step 7: Face to Face - Kissing!
Step 8: Hand to Head Love
Step 9: Hand to Body Desire
Wait--aren't there supposed to be "12 Steps to Intimacy"?
Yes, but I write clean romance, so the PG rating stops here.
There's a lot of info about developing romantic relationships naturally. One of the blogposts I like relates the steps of intimacy to character conflict. It's on COWBELL at https://jennyhansenauthor.wordpress.com/2011/11/08/using-the-12-stages-of-physical-intimacy-to-build-tension-in-your-novel/
This goes past the PG rating so read with care.