Suppose your kids figure out that if they ask you permission you're likely to say no. So they just say "oh, it's an emergency, there's no time to ask permission, I need to make a decision right now" and go and do whatever they want.
That's why Trump keeps declaring emergencies. The US has so many emergency acts that the president can give himself most powers, including ones that are explicitly forbidden in the US constitution, just by saying "it's an emergency" in an executive order. It's also not just Trump. No president since Roosevelt has been able to resist using emergency powers.* Trump's currently got fifty some on the go.
* Ford, Johnson, Kennedy and Eisenhower didn't make new emergencies, but they did continue their predecessors'.