You make some valid points, kerokerocola, but you have to consider picks, item buys and what is actually behind them.
Lets take caitlynn for example. What does caitlynn do in lane?Shes a lane bully and an Hyperlategame Carry. What are her benefits? She has
1. Long rage AA and Poke
2. 2 Spells with aweosme AD scaling aswell as passive.
3. An Escape with built in slow, aswell as a trap wich stuns briefly.
Considering these things you want to bully lane and not sustain, you simply wont need it an it is not worth the gold/the style of caitlynn.
Preffered first item untill this point:IE. Why? Because your long range makes saves you from taking a lot of dammage aswell as an escape.
Untill now it was of a champion perspective of view why you should build what you build first.
A different Example:Vayne.
Preffered first item by almost any Vayne player :BOTRK.
Niche Firstitem:Bloodthirster.
WHy should you build what. Botrk for 1vs1 dueling, High Health Oponents, Kiting. The three points mentioned are the specialties of vayne even before BOTRK and this item just enhances it.
Bloodthirster: Squishy enemies, Snowballing lane and game, Better teamfighting.
BT is better for the mentioned points , since BT makes vayne scaling with PD, IE way better than BOTRK. Also you wouldnt need mroe then 3-4 shots to 100-0 Squishies with BT-PD opposed to BOTRK/PD.
Conclusion: Every build is situational, are you snowballing?Losing hard? WHo are your opponents and what are your goals for laning phase. All these things ultimately decide the outcome of your build.
I do agree BORK is core, but I disagree that it should be your first item. If they have a tanky mid like Cho or a tanky support like Taric, BORK might do you well... but otherwise, her AA + Q combo is so strong that I almost always rush BF sword as my first item. Unless something goes really wrong, I almost always have enough gold for a BF sword.
Also, the "high HP" champions vayne faces usually end up a part of the equation mid-game, not in the lane. Aside from being able to land some attacks on their jungler, BORK's passive won't proc any extra damage than a straight up BF sword will. Again, this is another reason to wait for BORk for mid-game.
Then, since BORK is core, I might build a couple of longswords (even before scepter). It takes 2 longswords for a BORK, which is 20 attack power you can prioritize before you start building the ASP or the lifesteal. Plus the longsword it takes to build a Bloodthirster, and you can prioritize 30 total damage before you can prioritize the general utility stats.
In short, I really try to maximize my autoattack power by 20 minutes. ASP and lifesteal are better suited for autoattacks.
Again, damage helps with last hitting, returning trades, and obviously with DPS. Vayne is so mobile that you don't really end up harrassed as much as people tend to think.
By the way, I don't think of Cait as a "hyper-carry." If anything, she is one of the least-hyper carries lategame. She has no steriod, her lategame attack speed was nerfed in like July, and her Q and R actually take away from her DPS lategame. On the other hand, the real "hyper-carries" include Vayne, Tristana, Kog, and Jinx.
Vayne: Steriod from her ult that adds DPS without wasting time in between attacks.
Kog: Steroid from his W that adds a ton of range, steroid that also adds % health damage
Jinx: Steroid from her chaingun, range from her rocket. Her ult doesn't sacrifice time because it is an instant cast.
Trist: Steroid from her attack range and speed. Ult is also isntant-cast.
Of course, there are many others. Corki has a lot of burst for a carry, especially lategame. Twitch's range increase is OP. There are a lot of others, but I think "hypercarry" belongs to the ADC's who have a specific steroid that really increases their lategame damage per second.