When did club fitting become the norm for pro's?

The passing of Arnold Palmer got me to thinking about the equipment some of golf's elder statesmen played with.

Did these guys just play standard clubs their entire careers or did they take advantage of fitting and custom clubs later in their career or life as it was more readily available?

I mean, guys like Tiger, Sergio, Phil, etc and onward have been able to take advantage of custom built clubs their entire careers, fit to them.

When did the previous generations of golfers begin to take advantage and did the guys who had never hit a custom club switch from the length, lie, loft, etc that they'd always played?

Arnie had his own workshop and was notorious for the time he spent building/tweaking/customizing/perfecting the clubs he played. Even way way back before Arnie most of the pros were playing customized clubs, whether they modified/built em themselves or had them done by other craftsmen. One famous example was the invention of the sand wedge. Gene Sarazen came up with the idea and built/used one while playing the tour successfully. Others soon followed suit due to Gene's success.

I would guess clubs have been getting modified either for or by players as long as they have been produced. Just nowadays its much more accessible.