The targets for this malware are laypeople with enough funds to pay the fee but not enough to go after the creators. Hypothetically, if a national government or

The targets for this malware are laypeople with enough funds to pay the fee but not enough to go after the creators. Hypothetically, if a national government or other agent with sufficiently deep pockets were infected they would first attempt to crack it, failing that they would go after the creators directly- they would not pay the fee. So implementing weak crypto dramatically lowers the risk of prosecution or worse for the attackers.