I'll start by saying that investors have the advantage in negotiating experience and negotiating skill, so in most cases it is to the company's advantage to simplify the negotiation. Just as complex derivatives disfavor the less sophisticated party to the transaction, so also do complex equity instruments.
Liquidation seniority on preferred stock is fair, but I I've never been persuaded of a good reason for all the other complexities that find their way into term sheets and contracts. On the other hand, I've lost quite a bit of money to those terms, because founders carelessly agreed to them.