Mike, I think you'll find a pretty split mix of opinions on "do I" or "don't I" need tire warmers. As with anything of this type, it really comes down to whatever each person can afford, and desires doing with their own riding/racing program.
During the first 9 years of my roadracing, I did not own a generator or tire warmers. This consisted of racing year-round the first couple of years, including racing at Willow Springs in February, where the outside temperature was in the 30's in the morning. During those 9 years, I only had one "cold tire" crash, and this was a 1st lap of practice, 1st real corner, brand new tires, slippery old Turn 2 @ Sears Point "newbie" error.
By learning from that mistake, and subsequently religiously recognizing the need to perform a gradual and effective method of easing my tires up to temperature on track, with limits on applied lean angle reflective of that temperature change, no further cold tire issues surfaced.
The cold tire crash horror stories that flooded the racing community, with the intro of some notoriously "slick when cold" race-compound DOT tires from a particular manufacturer (about 6 years ago) finally pushed me into the $1,000+ expense of a generator and warmers. Since then, as that I have the equipment, I've used the warmers during racedays where I felt there has been some value in doing so.
As to your question Mike, of "do you need warmers", my opinion (FWIW) is as follows. If the outside temperature at a trackday/race weekend is in the 70's and above, there's no reason that a consistent application of intelligent first-lap track-to-tire friction warming of your tires won't do just fine.
Anytime the outside temps get down into the 50's (or below), it requires a much higher level of discipline (and "feel") to ensure that those first few corners on the warm-up laps are taken "slow enough" to not have any traction issues (aka "cold tire crash"). It's at these sub-60 degree trackdays/race events where I do feel that IF a person can afford to have a generator and tire warmers, there is an actual safety value to be reaped from their use. Can a rider avoid cold tire crashes while attending trackdays/races where the temps are in the 50's and below, despite not having tire warmers? Absolutely, as long as the rider learns safe and effective on-track tire warm-up techniques, and maintains the discipline to resist temptation of trying to go too fast - too soon.
Tire warmers, do you, or don't you? You make the call.
