It's down to a risk of allergies, possible contamination and an ambulance chasing industry that has become gorged and greedy on its own success. I could see the way the wind was blowing back when I was a student nurse as the industry had only just started to expand and because of that we weren't allowed anywhere near a ward until we had at least £1 million personal indemnity insurance.
Yes, when a hospital fucks up then they should be held to account but the massive payouts that these companies go for can completely destroy an operating budget so now anything even vaguely risky that can be stopped is advance is now banned.