Buffalos and land - sounds like a very expensive affair. While i agree with you that engagements are unnecessary, i feel that upholding traditions and rituals are important too.
I agree with @beverlyjoe that the engagement should only Last a short duration, and i think you should only be engaged if you are very sure you are marrying tht person.
I personally did not go through engagement, not sure if there is one in my culture too. But i considered the day i accepted the proposal as the start of the engagement hehe.