When does a poorly defined tabby pattern on a common color become undesirable to a breeder?

Answer

When the pattern is poorly defined

A poorly defined tabby pattern on a common color might be undesirable to a breeder, contrasting with a perfectly patterned Chocolate Tabby which seems rare because it embodies an appealing combination.

When does a poorly defined tabby pattern on a common color become undesirable to a breeder?
rareÇatcolorbreedDevon Rex