Let's face it. The reason we learn guitar is to play actual songs. No one in their right mind takes up guitar to play boring old scales. In my first few years as a young teen I learnt many songs and most sounded pretty bad. I couldn't understand why the kid down the street (let's call him Jim) who started later and was 5 years younger was improving at a faster rate. When we jammed he somehow made the song sound more like the actual recording. I needed to know his secret. Well it turned out he had a teacher where I was trying to teach myself. I actually had more experience on the guitar than Jim yet his technique, feel and sound were superior. So I enrolled with Jim's teacher quick smart and within months my playing took off. The reason was mostly to do with motor skill development and that meant scales. I had plenty of songs and riffs up my sleeve when I started lessons but my motor skills were poor. My teacher was able to transform my playing within months through skill development exercises focused around playing scales.
Developing motor skills
Motor skills are basically learned sequences that with enough practice become automatic such as brushing your teeth or tying shoe laces. Let me use an example. We can almost all relate to the skill of typing. My guess is around 80% or more of people who go out and buy a computer never actually learn to type. Most then spend anywhere from one hour to 10 hours a day on a keyboard yet still never learn the actual skill of typing and as a result become at best average typists using one or two fingers out the possible 10 digits at their disposal. They literally waste hundreds of hours every year because they take 5 times longer to type something compared to someone who has mastered the skill of typing. Many people also get RSI injuries as a result of poor typing technique. Why? Because all we want to do is write emails. We don't want to learn to TYPE! How boring. Sound familiar? Learning to type like learning guitar requires boring exercises much like scales.
All play and no work
Now it does seems kind of ridiculous not to spend a few months learning typing to save hundreds if not thousands of hours over a lifetime. This is exactly what happens if you just learn songs on guitar while ignoring the scales (motor skills). I am not suggesting you won't become a good guitarist just playing songs. It is quite possible if you practice enough but like the person who doesn't learn to type you will just take a lot longer to do it and it will usually end up wishing you did. Just ask any experienced guitarist. Develop those motor skills and I absolutely guarantee you will never regret you did but skip the skills and you probably will regret doing so.