but at the same time has enormous kill potential in lane
Ha.
No, she doesn't. She has amazing zoning potential, she has amazing poke potential, she's very solid at pushing opponents out of lane and is pretty much guaranteed to win a CS war.
She has almost no kill potential by herself though.
You have to derp out fairly hard for Caitlyn to actually get some kills in lane (not backing when you should), all her ability damage has such a long casting time she deals more damage with just auto-attacking, which puts her at a serious kill-potential disadvantage to anyone with near instant-cast burst and/or auto-attack re-sets. Which pretty much everyone else has.
She's oppressive and strong in lane, but she gives you plenty of warning before she's capable of landing a kill. Add in Heal, Barrier, and support skills and she can only finish someone off with her ultimate she could have finished off with a single auto-attack.
So why not lock it In as a DEFENSIVE tool except in situations where Caitlyn is placing herself strategically to outplay opponents?
90 Caliber net is already much more of a defensive tool than an offensive tool. You extend the gap and slow someone when it's used defensively, you just slow someone or close the game when it's used offensively.
With how unimpressive Caitlyn's burst, re-set, and AD steroids are it's also pretty risky trying to chase someone down with her escape. Caitlyn will not win a face-tank fight against pretty much anyone, she needs to out-range them to really win in most cases.
She's not like Ezreal where she can burst someone to 50% the moment she gap-closes at any rate. She's also not like Corkie where she can damage opponents while stunned.
Also - forcing it to target an opponent would massively reduce it's escape power. Wall-jumping would have a lot of cases where it went horribly wrong, and pretty much impossible against relatively skilled players putting Caitlyn in a situation worth escaping from.
Every other carry with such a fast dash (Lucian, Graves, Quinn, Ezrael, Trist at early levels, Corki considering that his Gatling gun is an essential tool for lane trades) makes up for it with a low range.
550 AA range isn't exactly low, and you really need to consider abilities for the overall range of a champion.
I mean - Ezreal certainly doesn't feel short-ranged, neither does Lucian or Corkie. They have really powerful poke skills capable of reaching quite far, and that skill damage isn't particularly low either. Considering Tristana's mobility has an explosive boost during team-fights I don't think you can realistically say she gave up range for it either.
As a class marksman are generally ranged and mobile.
