Because when you are thinking about the problem, your attention is focus on what you DON'T want (the problem) rather than what you DO want (no problem).
The absolute fastest way to make any problem disappear is not to think about it at all. The moment you quit thinking about the problem, the answer to the problem will appear in your mind out of thin air.
If you can't quit thinking about your problem then turn it over to someone else to solve it for you. It is always easier for someone else to solves our problem for us rather than ourselves. Why?
Because problems are uncomfortable and as soon as we resist being uncomfortable we become attached to the problem.
Once we become attached to the problem, it is not possible to solve it until we let go of it. Other people can solves our problems for us much more quickly than we can because they are not attached to them. They have objectivity about our problem that we do not have therefore they are able to clearly see solutions to our problem when all we are able to see are obstacles and roadblocks.