Because jobs with the BLS classification of 15-0000 are the ones that have the current H-1B dependent employers and make up the majority of the applications in the lottery.
https://www.gao.gov/assets/a314508.html or https://www.gao.gov/assets/gao-11-26.pdf
Most employers that submitted petitions to Homeland Security were
approved, and most were approved for one H-1B worker, but a small
percent of employers garnered over one-quarter of all H-1B approvals
between fiscal year 2000 and fiscal year 2009. Over the 10-year
period, about 94 percent of all submitted petitions (initial and
extensions) were approved, with a high of 97 percent in fiscal year
2006 and a low of 84 percent in fiscal year 2009.[Footnote 33] With
respect to the number of approved workers per employer, 68 percent of
employers were approved for 1 H-1B worker and about 99 percent of all
employers with approved petitions (627,922) were approved for 100 or
fewer workers. However, over the decade, less than 1 percent of all
employers with approved petitions were approved to hire almost 30
percent of all H-1B workers.
https://www.congress.gov/crs_external_products/IF/PDF/IF1289... During FY2022-FY2024, approximately 13% of employers
indicated on their LCA filings that they were either H-1B
dependent or were willful violators. However, most of these
employers planned to hire only exempt H-1B workers. Less
than 1% of employers filing LCAs indicated that they were
required to comply with the additional attestation
requirements.
The system that works for most other employers is being abused. Changing the system that helps staff rural schools and hospitals to one that benefits Big Tech because of body shops hurts everyone else.
Again from the GAO:
Restricted agency oversight and statutory changes weaken protections
for U.S. workers: Elements of the H-1B program that could serve as
worker protections-—such as the requirement to pay prevailing wages,
the visa’s temporary status, and the cap itself—-are weakened by
several factors. First, program oversight is fragmented and
restricted. For example, the Department of Labor’s review of H-1B
applications from employers is cursory and limited by law to only
looking for missing information and obvious inaccuracies. Yet a recent
Department of Homeland Security study reported that 21 percent of the
H-1B petitions they examined involved fraud or technical violations.
This is where the changes should be addressed. Making sure that the DoL has the funding, staffing, ability to audit.
Strengthening those abilities for BLS classification 15-0000 jobs rather than trying to rewrite H-1B for everyone is likely easier to accomplish.