That's a good point Six jours-- flipper shifters, mounted on the down tubes, bar ends, or handle bars, are a very good value for the money. Here's a sample build prce list.
8 speed bar end shifters-- $60
Deore rear derailer-- $30
Front derailer (Sora) $20
8 speed cassette & chain $35
total drivetrain cost-- around $150
A set of 105 brifters costs $200 alone!
Both systems will work for long time, but flipper style shifters last a long, long time.
Factoring in the life of the parts... flipper shifters are really a better value.
But riding STI is cool.....I can't blame anybody for having it.
I'm just too poor/cheap to do so myself.