item questions...

how come there are AP pen boots but no ad pen boots sure i can run faster and attack faster as an ADC but what if id like to run faster and hit harder also? imo there should be ad pen boots

also, how come last whisper ignores 35% armor while void staff ignores 30% MR? seeing as most tanks build more armor than MR 35% becomes significantly more than the 30% offered by void staff (not at all saying void staff is too weak)

also, how come there isnt an MR version of thornmail? high MR stats from a single item with a portion of the dmg returned to sender

also, how come the abyssal scepter looks so weak compared to a zhonyas? zhonyas has good armor, an awesome active, and a whopping 40 ap more where the abyssal has no active, less ap and its passive doesnt make up for the active AND loss of ap, one or the other sure, but not both. and please dont say its because one is cheaper than the other cuz thats my next question

just because abyssal is cheaper does that make it ok to be weaker? shouldnt they both be priced/have more comparable stats?

if the answer is super obvious to you then please just explain and not be troll, the knowledge will also help others im sure and we could end up on your team at any time so the more we understand items and their reasons for being (not just that they are) the more we can take advantage of our builds and our enemies builds

thank you