That's completely dependent on the application. SNMP over TCP would be a net loss because 1) it doesn't buy you anything as SNMP doesn't have any requirements that TCP meets above what UDP provides, 2) TCP would be exceedingly expensive, requiring connection buildup and teardown, ACKs, etc., and 3) it's way easier to implement UDP than TCP, so dumb devices basically need to only construct a single Ethernet frame to make it work.
Many, many applications deal much better with loss than they do with delayed retries. You don't want a VOIP app to perfectly recreate what the other part said 30 seconds ago, games usually only care about current state, and so on. In many of those cases, TCP is the wrong choice but a lot of people use it out of familiarity.
Remember, UDP came after TCP. One isn't "better" than the other and they serve different requirements.
Many, many applications deal much better with loss than they do with delayed retries. You don't want a VOIP app to perfectly recreate what the other part said 30 seconds ago, games usually only care about current state, and so on. In many of those cases, TCP is the wrong choice but a lot of people use it out of familiarity.
Remember, UDP came after TCP. One isn't "better" than the other and they serve different requirements.