Nicotine is a skin irritant. It's basically the feel of nicotine hitting your throat as you inhale. And usually the warmer the vapor the more TH too. Too much can lead to sore tongue and throat and even lungs. Many prefilled carts and and multi-brand hardware vendor juices are the 100% PG Chinese juice. PG lets through the most nicotine TH. For some those juices are too harsh. Having some VG in the ratio (example 70pg/30vg) dulls the TH a bit and is usually enough to keep the nicotine from causing soreness while still letting through a decent amount of TH. People need to find what balance they like of PG/VG with their nicotine level and their PV model. I think having some amount of TH helps simulate the feeling of smoking.
There are some flavors that give a throat sensation which can enhance or somewhat replace nicotine TH (for 0 or low nic juices for example) - mints, menthols, cinnamon and other spices, and to a lesser extent vanillas and some other flavors have cool or peppery throat sensations. Qhit (an additive) or a bit of edible alcohol like gin or vodka or grain alcohol can also add a hit-like feeling.