People’s brains develop the most when they’re young. Children can pick up languages with ease if they’re being spoken in their homes growing up. Also, despite how over-programmed many have become in this day of after-school clubs, sports, homework and the like, they tend to have ample practice time. Because they’re in school they’re used to learning. In a way, it’s like one more subject they’re acquiring. By the time they’re in their teens or adolescence they should hopefully be capable players with the ability to entertain friends and achieve a good amount of fulfillment. There are certainly benefits to starting young.
But starting later in life has many positives. For one thing, your fingers have developed to their full size and strength. Everyone experiences a time of adjustment where their fingers get used to staying in relatively contorted positions, and waiting for your fingers to numb to the feeling of constantly pressing down metal strings is easier to do when you’re of age. Beginner’s always feel it’s difficult to reach across six strings to do even basic chords, but at least after your fingers have finished growing you know it’s possible!
Also, presumably the decision to play comes from a strong place of desire, and the experiences from accomplishments in other places in life can be used to bolster perseverance. Playing music can be rewarding later in life, and is often therapeutic or even cathartic after a hard, stressful day of work.
All that’s needed is a genuine desire to play and a willingness to persevere to make it happen. It can be frustrating not being able to produce beautiful tones right away (or even half decent ones), but patience is something learned with time. Adults are well suited to this. With age comes the understanding that real beautiful things take time to develop. It’s understood that if guitar could be learned in a day we’d all be guitar players. Children have activities hurled at them, but this isn’t quite true as you get older, and so with age comes a certain seriousness.
While it’s true that musical prodigies are identified at a young age there are more and more people these days trying guitar later in life. Whether it’s something they’ve always wanted to do, something that’s suddenly become appealing, or something to check off the bucket list guitar talent knows no age limit. Besides, it’s not as if guitar only rewards those who reach a certain skill threshold: so long as it’s something that gives you pleasure there’s no reason not to play! The satisfaction playing music yields is unparalleled. Everybody should experience this in their lifetime, no matter how old they are.