Andrew: I think a few that are missing from this Five, and not all of these apply to later versions of NBA Live / NBA 2K are:
1) The "I Need the Roster Space" trades
: In NBA Live, at least up until 2008, you could not draft a player if you had a full roster, and you could not release a player in the off-season. In order to get something in return for my investment, I would try to create roster space before the trade deadline by packaging two for one or by trying to take on a crappy, but expiring contract. For Live 07, this often meant taking on Adonal Foyle, Jerome James, or DeSagana Diop. If memory serves me correctly, I think that Calvin Booth also had a bad contract, but that may have been an earlier iteration of Live.
2) The "Let Me Resign My Player" trades
: Similar to what was mentioned above, this was often a matter of taking on expiring contracts in order to make sure that you can resign the players that you want to keep on your team that do not have Bird Rights (for whatever bizarre reason). This may include rookies that were acquired in off-season trades, or players that had long standing with your team, but bizarrely no longer had Bird Rights. It would often be the case that I would find two players that I absolutely wanted in the draft, or miss out on the one player I wanted by a pick or two; however, if I acquired them in a trade, I wouldn't be able to retain Bird Rights by the end of their contract.
3) The "He's a Real Player, I Need More of Those" trades
: These trades would often come down to being ten seasons into the league, and suddenly lacking real players. I remember a Franchise Mode where I took on Andrew Bynum and Andray Blatche and tried to turn them into the next Twin Towers. However, in trying to improve them, I focused a bit too much on trading for players to complement them. I forget how, but I ended up losing either one or both of them, and I was stuck with one season of created players in whom I had no training or emotional investment. Pretty soon, I was trying to get some of those players that linger around forever. such as Nikoloz Tskitishvili or Julius Hodge, just to make it interesting for me again.