There is a cultural aspect to tanning also, and it goes in and out of fashion like anything else. A tan used to be looked down upon as low class and characteristic of people who labored outdoors at menial jobs, while being pale was in vogue with high society. Back in the 70's and 80's, a tan became associated with leisure, vacation, and people who spent time outdoors having fun, while being pale became associated with people who stayed indoors and had no life. I lived in coastal southern California for much of my life, and by the time I left about 5 years ago, parents had become almost comically hysterical about their children going outside for any amount of time without putting on sunscreen.
In the 1950s and into the '60s I remember that acquiring some color in the middle of the snowy northern winter might be called a "Florida tan". Because decades earlier a Florida trip had become one of the few ways average Americans could experience summer temperatures & sun when much of the country was bundled up against the cold for several months.
It also implied you had at least some disposable income to spend on the luxury of a distant vacation, and the free time to take it. And Florida was one of the few places in the US where you could find warm sun, sandy beaches with pleasant ocean water temps, and an entire infrastructure built around tourism. Definitely a social status marker for White people to bring that tan back home.
It's true you could use sun lamps at health clubs and some beauty salons even in the 1930s, but they were almost exclusively in larger cities, and a luxury indulgence mainly for the wealthy. Unlike today, when spas are more affordable and widely available.
My grandmother had her own home sunlamp, a large floor mounted contraption. It was stored in the attic after her death, and later in my teens I had one of my signature misadventures trying to use it. Suffered some serious burns that took months to heal, and nearly 2 years for the scars to fade.