And therefore, they must "work" at "least a little," right?
Please check my answer elsewhere on this forum for "What is the best laser for skin resurfacing?" I will include edited parts of the answer here for your review.
I have taught laser surgery, including resurfacing, for over twenty years, nationally and internationally (Korea, Canada, Caribbean), and have performed thousands of laser cases in my practice. (I am in private practice, and do not have academic affiliation, rarely publish, but have taught nearly a hundred laser courses and thousands of physicians of various specialties over these years). Now, just the facts, Ma'am.
Ablative CO2 laser resurfacing came first, gave great (dramatic) results for both wrinkles and acne scars, but fell somewhat out of favor as hypopigmentation (skin color lightening) occurred a year or so after treatment. Wrinkles, spots, and sun damage still gone, but line of demarcation where treatment stopped, and lighter skin color where treatment was done. Bummer!
Ablative Erbium-YAG laser resurfacing came next, but treated much more superficial layers, so skin healed faster, with less redness, but with less dramatic changes, especially for deeper issues such as acne scars. If the doctor promoted this as "better than CO2" and charged as much, patients were unhappy, but not because the laser had a "problem" other than milder results. Bad doctor "marketing!" These lasers are now being "repurposed" as "micro laser peel" machines because of the superficial nature of the tissue removal.
By the time that third-generation combination CO2/erbium-YAG lasers came along about ten years ago, the herd of dermatologists, plastic surgeons, and other laser doctors had moved on to the "non-ablative" lasers or therapies such as Thermage, N-lite, Cool-touch, Smoothbeam, and many others. These all "worked" to varying degrees, but usually with very minimal results, and virtually NO improvement with acne scars. Prices dropped, and so did most of the hype, and "the herd" of doctors that need the "latest and the greatest" moved on to Fractional lasers. (Very few of us--usually the experienced instructors--bought the third-generation CO2/Erbium YAG resurfacing lasers. Even though they work the best of the three generations of lasers discussed thus far, slow sales = company bankrupt.) The rest of the herd was at the fractional laser rodeo!
Fractional lasers started with Erbium wavelengths, and treated the skin in tiny polka-dots. Bridges of intact skin were left untreated, which is said to promote faster healing and less down-time (partially true). Actually, less skin treated = less result, which required multiple treatments, which = more procedures, more healing and MORE cumulative downtime. Oh, and the total cost adds up to a tidy sum usually! The results are real, but with superficial layer and polka-dot treatment came mild results. More, give us more!
The next fractional lasers returned to CO2 wavelengths, which penetrate deeper, and still treated skin in tiny polka-dots. Fortunately, unless the energy was turned up too much, or the polka-dot density too tight, hypopigmentation changes were limited, and the results were indeed better. Still only in the fraction of the skin treated, still requiring more than one treatment for results that could approach that of well-performed third-generation combination CO2/Erbium-YAG ablative resurfacing (which very few doctors even had then, or have today), and still adding up to a tidy sum for only "fractional" results. BTW, it still takes a week to heal fractional laser treatments, and if you add up the time for multiple procedures, doctor's visits, and cost, HOW can this be "LESS DOWNTIME"?
So at the risk of being contrarian, I would submit that a properly-performed ablative CO2/Erbium-YAG full-face laser resurfacing remains the BEST one-time laser resurfacing procedure available, especially for acne scars. With proper skin care, I routinely have patients healed in 7-10 days, and with minimal (truly) redness easily covered with standard make-up. I even purchased a second CO2/Erbium-YAG laser for parts--they are no longer available. But the marketplace delivers what the public (and their doctors) demand. I know from all the courses I have taught over the years, that many, if not most, of the doctors that use lasers don't even understand the basic laser biophysics of how laser energy interacts with tissues--they just want to know "what is the basic setting, where is the trigger, and how much can I charge?"
Even when I "gave away" free treatments with non-ablative laser devices when I evaluated them years ago, barely one third of patients saw even minimal improvements. If you like the emperor's clothes, I suspect that you may well be one of the minority who like the results you see on acne scars by non-ablative laser treatments!
Enough said, my soapbox is sagging! Caveat emptor!