My 2psi:
This may be a bit rambling, and for that I apologize in advance. If I say something you don't like, or agree with, or think is just plain wrong, please know that I really don't care.
And, yes, the following is in lead-up to the OP- post.
There is no law (at least in the USofA) that I am aware of that says you have to be certified to dive for recreation, or to have your scuba tank filled. An industry standard? Sure. But no law, statute, regulation, etc... I believe industry standards are generally a good thing, as the overarching (underlying?) purpose for such standards is to promote safety (and apparently to draw the line for establishing compliance with a standards of care for negligence in legal actions

). Such standards do not ensure safety mind you, but do - at least attempt to - provide a baseline for competent skills upon which safety is based.
I have known a number of highly competent divers who never got around to being certified to dive. One had his own boat and compressor. Another became a scuba instructor without ever obtaining any kind of dive certification before taking the ITC. I currently dive a lot with a guy who started diving in 1963 but is still not certified. The guys at the local dive shop just see him regularly and assume he is certified and he gets airfills all the time.
Now to the OP's post re: "Do you believe that from a safety stand point, it is necessary to get certified if you plan to stay in the 40 foot range?"
Well shoot. If one is using 'necessary ' in the context of its a really good idea to at least get the basics down as set forth by industry standards so you stand less of a chance of death or serious bodily injury, then YES, it is necessary. If one is using 'necessary ' in the context of I'm a smart person and there is no reason I can't get the info from a book or on-line and practice with a friend, then, depending on the background of the person, NO, not necessary, but still a REALLY GOOD IDEA.
The latter statement is qualified in that it also very much depends on the person. A lifeguard, or surfer, or swimmer, or long-time snorkeler with excellent watermanship skills and knowledge is more likely (on average) to not panic in a watery environment than a person without those underlying skills. I dove a lot for 9 years before I took a PADI Basic class and obtained a cert. But I was born into a ocean-oriented family and had my dad who was a YMCA swim instructor, but not a scuba instructor, teach me how to dive. I would not have felt comfortable doing what I did if dad hadn't kept throwing me in the pool before I could walk.
Bottom line? There will be those that can become competent safe divers on their own without obtaining a certification. However, it is my opinion that for the vast majority of folks out there certification is really a necessity for a foundation as a safe diver.
End of rant. M