You're right regarding safe locking - it's rare to have a station on ANY transit line where it's safe to leave your bike. Yes, I got away with it a couple of times in Folsom, but that's a fairly well-policed and low-crime area. Most places, if a bike is there every day for more than a day or so, it's considered a scrap source either by cutting the lock(s) or by stripping in place.

Most transit lines that encourage bicycle riders have a bunch of lockers for rent by the day (some automated systems) or the month. Most of the time, there's a long waiting list for the monthlies. Most people don't have a place to put a bike at work, so just taking it with you (assuming there's space on the train or bus) may not be an option and certainly isn't convenient. When doing that, I could also use the bike (still 4c/mile DGS reimbursement rate (taxable!) like it was when Jerry Brown started paying bike mileage in the 1980s!) for work trips in town but beyond reasonable walking range.

BTW, have you priced bike lockers? The do seem to be priced for the market of government agencies or corporations responding to some government mandate ... some examples for those who might be shopping (thank you DuckDuckGo) ...

[www.globalindustrial.com]
[cyclesafe.com]
[ameribike.com]
[www.reliance-foundry.com]
[www.durabikelocker.com]
[www.urbanracks.com]