FWIW, my 30' "Classic" boat, like many others of similar vintage, doesn't have lifelines although I have the option to fit them for going off-shore. Instead it has a 4" ankle-high bulwark fitted right around the deck and I'd suggest that, given adequate hand-holds, that the bulwark gives at least an identical feeling of security (if not more so) than having lifelines.
If you do have lifelines fitted, aside from the "going overboard" feeling*, although, yes, they DO help hold the headsail on deck when dropped, having to skirt the thing on every tack - meaning someone going forward hence increased possiblity of them actually going overboard - is a major pain in the butt. JMO..
(*) Most yachts less than 60' LOA don't have very wide decks. When walking along a deck with lifelines fitted you can feel them pushing against your legs, which is why people feel they might go overboard. This is because the lower body is constrained inboard whilst the uppper body can move outboard making you feel that if you lost your balance due to some unexpected movement, you'll be swimming. With a bulwark or similar *high* toerail to ankle height and NO lifelines, the feeling of security increases
, simply because your legs are free to move to help you balance naturally, whilst the bulwark prevents your feet from sliding on a sloping deck.
By comparision, I often race in an Adams 10 which has only a small toe-rail (and in some places nothing at all!). Having nothing to stop you going feet-first on a sloping deck makes for a HUGE feeling of insecurity in a seaway compared to having lifelines.
In summary: IMHO, for sailing on enclosed waters on a small boat, optimum feeling of security and practicality is found with an ankle-height bulwark and hand-holds along the side of the cabin and center foredeck. Next best is lifelines and worst is nothing at all..
Off-shore in a blow, you need lifelines to keep EVERYTHING on deck (not just the crew) and that's really all there is to it.
Hope that helps.