Anyone can learn to paint and draw better but not all will become selling artists. Mastering the skills doesn't make you creative. You could become an illustrator, but not necessarily a creative artist.
It is similar to music. You can learn to play an instrument very competently but that doesn't mean you can become a successful composer.
I also think publicity and marketing play a big part in how many artists become successful.
If you want to improve your own painting techniques, why not contact your local art club. Many, like ours, offer tuition courses and workshops in a range of media - not just in watercolours.
Incidentally, watercolours are harder to use than say acrylics but are for some reason more popular with beginners.