To answer your question, No , its not *needed* to push non-critical patches, but if you have a downtime you might as well push all patches.
Here are the general guidelines,
Abstract from KB http://kb.vmware.com/kb/2014447
Critical - A problem which may severely impact the customer's production systems (including the loss of production data). Such impacts could be system down or HA not functioning. A workaround is not in place.
Recommendation: Immediately implement the critical patch.
Important - A problem may affect functionality, or cause a system to function in a severely reduced capacity. The situation causes significant impact to portions of the business operations and productivity. The system is exposed to potential loss or interruption of services.
Recommendation: Immediately plan for a maintenance window for the patch.
Moderate - A problem may affect partial non-critical functionality loss. This may be a minor issue with limited loss, no loss of functionality, or impact to the client's operations and issues in which there is an easy circumvention or avoidance by the end user. This includes documentation errors.
Recommendation: Implement the patch in your next maintenance window.
Low - A problem is considered low or no impact to a product's functionality or a client's operations. There is no impact on quality, performance, or functionality of the product.
Recommendation: Implement the patch at your convenience.