It's about intent.
I go to a bar to have fun and pick up chicks. One thing leads to another and we hit it off. We might have sex or we might not and we might end up married that night or 12 years. My intent can be colored by my desire for sex but it isn't my announced intent and it isn't her announced intent. I am also intrinsically stating that I am open to a further relationship if it works out.
The difference between that and an app is that with the app you chat a little and go through a checklist of questions maybe to gauge your comfort and compatibility level. You then schedule a time to meet up to verify attractiveness and basic chemistry. You then hopefully go and have sex. That is all that is expected and you both know it and you go into it with an implied contract of "in the morning we walk away if we even sleep over". Both people are stating that is their goal. If something else happens it is a rarity.
The bar scene and dating like that is most definitely with the end goal of at least a relationship. The tinder scene is most definitely the end goal of your dick getting bodily fluids on it and anything else is an accident.