Why is there such an aboundancy of PEAS and not so many tryptamines?
Because the chemistry required for synthesizing phenethylamines is much easier than that of tryptamines, both in regards to the skill required as well as the number of methods available for performing a certain chemical transformation.
It's also a question of economy, the starting materials required for the syntheses of many common tryptamines can easily cost between 10-100 times as much as the ones used for the most common phenethylamines - A quick look through the Acros catalog gives the following prices:
4-Hydroxyindole (for psilocin, etc): €118/1g
5-Methoxyindole (for 5-MeO-DMT, etc): €65/5g
4-Methoxyindole (for 4-MeO-DMT, etc): €91/500mg
Tryptamine (for DMT, DET, DIPT, etc): €44/50g
Indole-3-acetic acid (as above): €43/25g
Tryptophol (as above): €37/5g
Indole (as above): €35/100g
€1.00 = $1.15