I was actually thinking about this the other day because if you win your first promotion game and lose your next two, you'll be at LEAST two games away from reaching promotion again; whereas if you lose, win, lose, you will potentially be only one game away from reaching promotion again.
I understand the mathematical reasoning to this (i learned how to add/subtract when i was four yrs old) but logically it makes no sense. Basically, all our first win in promotions means is that we have a game to lose; which would be great if it impacted the conditions of our third game win or lose. Unfortunately that's not the case and we actually get punished harder for consecutively losing our next two games than we do get rewarded for consecutively winning (we enter the next division/tier at 0 LP even if we go undefeated in our promotion series). This is why we see gold 1 players with higher mmr than plat 5 players (the same example can be made of any two adjacent tiers).
I understand that climbing isn't supposed to be easy, but neither should be demoting; and losing 40-50 LP during what's supposed to be our opportunity to promote leaves us 3-4 losses away from demoting. It shouldn't be possible for us to go from promotion to demotion in 2-3 hours unless it's possible to go from 0 LP in one division to the next division in just as much time.