But those eraser-head helmets were just too goofy to accept. They block the user's vision on the sides, while leaving the "view" out the back wide open. (Why?)
Yeah, the actors were always turning their whole bodies sideways to look at anything. Just like the Bridge, with it's awkward knee-level railing and Spock's bend-over-to-see-in hooded viewer, the spacesuits were nifty-looking but ergonomically terrible.
We know from Ralph Senensky's blog that Bill Theiss delivered the spacesuits a full half-day later than they were needed. Theiss must have lost a lot of time that week casting about desperately for an affordable yet "way beyond today" helmet design that he could build four of.