This has been my experience with big tech companies as well. Many are willing to negotiate compensation, a few will negotiate holiday and benefits, but none of them will touch legal agreements like NDAs, copyright assignment and non-competes. And if you try the cute “cross off the terms you don’t like and initial them” trick, you’ll get a stern warning letter from Legal to sign it unmodified or GTFO.

A lot of the hiring people just don't have the authority to contact legal and request a change to an agreement because the implications of that change must be reviewed by expensive lawyers.