Because TVP has zero incitements of actually entering. Poland is not successful in this, there is not general public interest or artistic interest aswell. The Euro argument was just an excuse that came in the right time... but we'll see, I hope of course you'll come back.
But it has always been like this! TVP has never been "enthusiastic" about Eurovision, and they never made any announcements before September/October. As you're a Swede, it might be hard for you to understand, that not every country announces their participation immediately :? In Sweden, ESC is a very serious thing, in most other countries - it isn't. But that does not mean everyone will withdraw, just because they didn't make any early announcements.