While simply being a Bulldog Club member doesn't offer much in terms of personal benefits, there's a good bit that is based off of your priority point ranking.
1. Determines what seats you are eligible to get for football. If you look at the seating diagram, you'll see that certain seats require a certain donation. However, if you were to try to donate those amounts starting today, you'd have virtually no chance at getting those seats. The reason is that there are bulldog club members with a higher ranking that want the same seats. You have to accumulate BC points for some time before you can actually get the better seats. I know that you say that you're fine with the seats that you have and you don't care to move. However, what happens in a couple years when you have to donate a certain amount to get the same seats that you now have? You say, "That's fine. I'll just donate that amount at that time." Well, what if the AD also decides to hand out those seats by priority ranking and you have no priority points? If that happens, there's a good chance that you're going to get screwed. You may think that this wouldn't happen, but look no further than the Hump re-seating from 4-5 years ago, and this is precisely what happened. When demand is high enough that MSU can require contributions, you can bet your *** that they're going to do it.
2. Bulldog Club membership is just about the only way that you'll get basketball tickets during the better years.
3. Priority ranking factors into a lot of "special" tickets such as road game tickets, bowl games, postseason play.
4. Priority ranking factors into parking pass allocation.
5. Bulldog Club members get half off Maroon to the Max if you care about that. At least, I think that offer still stands.
So in summary, if you're good with your current season, parking, ability to get postseason tickets, etc, then there probably isn't currently a huge benefit to you. However, I fully expect there to be a rapid expansion of seats that require BC membership for football in the near future. If that happens, it may not mean that you can't get tickets, but I can just about 100% guarantee that you'll be sitting in one of the top corners of the upper decks.