Why don't you use an SPL (Sound Pressure Level) meter?

[Kurt C.]

The experts tell me that it is impossible to compare different components in a meaningful manner or accurately compare two speakers without carefully matching volume levels using a sound pressure level (SPL) meter, yet few people have or use them.
Sound and Vision's "How We Compare Speakers"
More info on using SPL meter and why it is important
The cheap ones only cost $40. Almost everyone who reads this forum cares deeply about how their system sounds, so why do so few of us have or use SPL meters?