Although it was through agency, when I resigned the high tech vent case I worked - they had a very hard time replacing me.
Maybe it is the vent aspect. Vents scare some nurses.
But I agree with another response - the problem may be with finding RN's. LPN's seem much more prevalent in private duty or home shift work. As a RN who worked home shift work for several yrs, I often got vibes that I was doing "an LPN's job". Frequently it was suggested I change to supervisory/management work. But I wanted shift work and did NOT want the hassle of management or supervision for various reasons.
Unfairly, I think RN's who do home shift work or private duty are considered to be losing their skills or stepping down. Many of the cases are very high tech! I actually gained new skills that I did not have from all my years of hospital nursing!