The Democratic National Committee (DNC) mandates that states have to hold their primary elections before June 9th, 2020, according to Rule 12 of the Delegate Selection Rules.
The Delegate Selection Rules provide that each state’s first determining step must take place by 9 June. If a state violates the rule on timing, or any other rule, they could be subject to penalties as prescribed in Rule 21, including at least a 50% reduction in delegates, which will need to be reviewed by the RBC.
Source: The Guardian
However, Louisiana and Kentucky both rescheduled their primaries to be held after June 9th, specifically on June 20th and June 23rd respectively. Kentucky rescheduled their primary to June 23rd even after DNC earlier warned Louisiana on its primary reschedule that "changing the primary to June 20th violates the committee's 'rule on timing'".
So, are there any practical reasons why must these states hold their primaries after June 9th, especially since it is viable to hold them before June 9th, given that a large number of primaries are currently scheduled for June 2nd.