While the tag-off system does suck, putting turnstiles at every station is probably not cost-effective. They only last so-long, are exposed to weather and abus

While the tag-off system does suck, putting turnstiles at every station is probably not cost-effective. They only last so-long, are exposed to weather and abuse. Depending on the layout of each station, you could even need multiple sets of turnstiles for a single station. Turnstiles for the LA Metro cost $46 million for 387 turnstiles.