In training my apprentice he mentioned that he could multi-task which also reminded me of my brother, who shares a similar belief. More so there is a saying “Jack of all trades and master of none”. This saying has many interpretations but basically they deal with focus. In short the less you have to deal with the more time you have to be better at that one thing.
It is also the way people think. We want to see a specialist. Someone who has dedicated their life to knowing all that can be known about our problem. No one wants to see a General Practitioner anymore. It use to be just doctors and dentists. Now there are surgeons who specialize in each and every organ! The brain, stomach, liver, skin, and even appendages like foot, hand, ankle, you name it there is more than likely a specialist for it.
The same is true in software. While we all write programs or functions or modules or (you give it a name) we are writers of words that computers will follow to the letter! It use to be you would hire a computer programmer. Now we specialize. There are web designers, game programmers, data base experts, and so on ad nauseam.
Our one man band shows that you can pick one trade and still be unfocused! One needs to develop a niche. He should stick to being a trumpeter, accordionist or banjo player. So to be successful be knowledgeable in one specific trade vs. trying to become a Jack of All Trades.