Additional Reasons for Drinking
The Chasam Sofer explains that the Jews in the time of Achashveirosh attended his seudah and got drunk. Therefore, we have a mitzvah to drink to rectify the aveirah which was committed at that time.
HaRav Shlomah Zalman Aurbach zt”l says that Purim was established during the time of golus and it is not possible to be joyous while we are in golus. Therefore, we drink to forget about the fact that we are in golus and then we can be joyous properly.
HaRav Moshe Shternbuch shlita explains that a sober person is aware of his true feelings and his surroundings, and uses his intellect to hide his feelings. When he is drunk and has no control over his intellect, he cannot hide his feeling, and his true essence emerges. Even without our intellect, we should be close to the Torah and choose the good.
