The polish government decided to use shock therapy because

To put a little bit of context:

'Shock Therapy' in this question refers to the rapid transition between communism into Market-Based economy that Poland did as soon as they got free from Soviet Union.

At that time, the mismanagement that Communist regime did caused an economic Slump in Poland. They made the government obtain control on all aspect of economy, leaving little freedom for the citizens to actually pursue their own interest. But, since the communism ideology was implemented for a long time, people's perception of what a working economy should be were heavily clouded.

The fast transition to a more liberalized economy was aimed to revitalized Poland's economy as soon as possible. They want to produce different types of Goods and Services to fulfill the citizens' need along with exporting some of those products to compete in international market.