In a word, money. Genshin actually began proceedings by only offering players a 120 Resin cap, which will still give day-one players nightmares. Hoyoverse had responded to low resin claims before and upped the cap to 160. However, we would say it's pretty unlikely that the company will tweak this again. After all, more Resin means less grinding, and less grinding means less spending on microtransactions. As much as we like to believe that developers want to look after their players, they also want our cash. So don't expect a Resin bump any time soon.