​​​​Explanation

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The solid lifter with preload spring ensures that the lifters' rollers are pressed onto the cams even when the valve is closed—i.e., during the valve clearance phase—and roll over the cam base circle. Without this feature, the rotation of the lifter rollers would stop during the valve clearance phase, meaning that the rollers would come to a brief standstill. During the next valve lift, the lifters' rollers would be abruptly set in motion again from a standstill and would briefly grind on the cam's start-up ramps.

It is comparable to a aircraft touching down on the ground with its landing gear extended. The tires are set in motion from a standstill to full rotation in a fraction of a second. The resulting smoke trails are caused by friction. It is easy to see that both the tires and the asphalt suffer enormously during this short phase.
The same thing would happen to the cams, and always at exactly the same place, namely on the cam start-up ramps. At 800 rpm, for example, this would happen 400 times per minute. It would only be a matter of time before the cams wore in.