Because TSA
1) changed long-standing policy to prevent checked bags being SECURELY locked (required nowhere except the U.S.)
2) took away the few plastic-wrap machines available in U.S. airports
3) yet refuses to commit its employees to the accountability level of quality-checkers in a third-world garment sweatshop routinely provide.

Thieves have ever been alongside the many honest baggage handlers; TSA eliminated pax' right to oppose them, thereby REDUCING security.

FTers must be tired of hearing this, but you must have missed it:

I've traveled since the early 1960s on every continent except Antarctica plus many islands, including places where one's mere presence indicates uncountable wealth by local standards, I took moderate precautions and never had a single theft until TSA instituted the unlocked-bag policy. Since then, and ONLY when flying domestically, I experience theft and/or damage several times a year—though I fly much less than others here.