I am an options trader that is rarely, if ever, delta-neutral because I am using the options to make directional bets on the move of the underlying instrument. I expend virtually 99% of my analysis on the potential direction, magnitude and resistance points of the price-move in the underlying. About 1% of my analysis is on the behavior of the options themselves in order to minimize slippage.
Using options to make bets on direction allows traders like me to benefit from directional price-moves with leverage without the capital required to reap the same benefits from trading the underlying instrument. However, it is not for the faint-at-heart because you are fighting theta (time-decay) every day. Whereas traders using the underlying can usually afford to be wrong a lot longer.
Market Makers are usually always delta-neutral because they are writing the options and making their money on the arbitrage between bid-ask or options quotes in different markets, among many others. They instantly hedge their positions (go delta-neutral) in order to protect themselves against option value swings that would erase their profit margin.
There are entire careers devoted to particular option trading styles. So, there are a multitude of opinions and theories. I just wanted to give you a snapshot of what I do.