You are silver 1 and you don't have Gold 5 MMR yet so you gain less than you lose. Your MMR is High Silver 2 / Low Silver 1. Since your next step is Gold 5 the system wants you to have Gold 5 MMR before it promotes you. If you gained more LP than you lost than it would be possible for you to get into Gold 5 with mid Silver 1 MMR. Even though MMR is hidden it is still the driving force and heavily influences your displayed badge my working as a gatekeeper for when you get close to promotions. Otherwise people could get into Silver 1, lose their 2-3 free games,, then get into Gold 5 with Silver 2 MMR and not actually being able to consistently play at a Gold 5 level, which is the requirement for hitting the rank.