new to mining questions

hi everyone, this is my first post on here as i just started mining today. i have 2 main questions im hoping can get answered. first one being that i know ethereum is pretty low currently. im using a 3080ti and at 70 ms/h its earning less than $2 a day. my question is if i keep mining and ethereum goes up, my previous earnings go up with it right? if thats the case, why wouldnt everyone keep mining regardless of the current value? my next question is regarding my gpu. is it worth paying around $200 more to return my 3080ti for a 3090? thank you for the answers