Are high efficiency speakers necessary?

What are the advantages and disadvantages of a high-efficiency loudspeaker? Why aren't all loudspeakers high efficiency? Have a question you'd like to ask Paul? Go to our website at http://www.psaudio.com/ask-paul/ I am getting close to publishing my memoir! It's called 99% True and it is chock full of adventures, debauchery, struggles, heartwarming stories, triumphs and failures, great belly laughs, and a peek inside the high-end audio industry you've never known before. I plan a few surprises for early adopters, so go to https://www.paulmcgowan.com and add your name to the list of interested readers. There's an entire gallery of never before seen photos too.