Answer: Prayer is an absolute and obligatory command for all the people. And even if we presume that one can avoid evil deeds even without praying, then too he shall not be exempted from this law. He must offer the obligatory prayers, because if this is allowed many people will get an excuse to avoid it altogether.
Apart from this there is no guarantee that one would be able to save himself from sins without prayers because prayer is the greatest medium of being attentive to the Almighty. Experience shows that people who do not pray, cannot be safe from any type of sinful acts. At least they are not particular about personal hygiene.
In addition to this prayer and attention towards the Almighty play a very important role in the perfection of faith and in the gradual development of spirituality. Abstaining from sins also contribute to the spiritual upliftment of man.
In any case, it is obligatory upon all able Muslim men and women, without any exception that they must perform the duty of prayers.