I don't see it as a necessity.. but it's one of the first "luxury" things I bought... then a chronograph. Like Larry338 said, you could probably get by by just twisting them in a piece of fine grade scotchbrite... tumbling just makes them pretty. I shot large bore pistol cartridges for a few years without ever tumbling them... they were pretty dark before I got my first vibrating cleaner...they still worked, though... It wasn't as bad with them, because I used carbide dies. On rifle dies, you could theoretically drag a particle of sand, grit,.... something, into the die and scratch it...

"Progress, far from consisting in change, depends on retentiveness..those who cannot remember the past are condemned to repeat it." Santayana