Well, you don't need a GF to have sex, so that can't be a pro/con. If you want to experience an intimate relationship between you and another human and what that can entail and what that is like, it's a chance for you to grow as a person and do things you couldn't even imagine were possible. But those aren't pros/cons either, because you can take drugs for example to experience the same hormone highs, you can grow as a person while working for example, and you can do things unimaginable without GFs.
So it comes down to time management, what people have for schedules or projects to take their time. Maybe condition program, maybe science, maybe a job, whatever. Is it imperative to have human contact? You can have human contact without GF.
Me personally I am in a relationship and the pros include: amazing sex, amazing person to spend time with, no stressing out over dating and failed dates and contacts, work together towards common or uncommon goals, grow as human beings. Cons include: less time, less freedom, a lot of work and drama, emotional baggage.