You have the cause and effect reversed. Body shops and US companies love hiring Indians over other nationalities precisely because they're much more likely to get stuck working for them for several years if not decades, and making them more money while suppressing wages, while other nationalities switch companies for higher pay etc. once they get their Green Card in a year or two. The body shops only exist and serve a purpose because the worker visa laws are worker-hostile and company-friendly on purpose to screw labor and benefit companies, for example according to the law workers are illegal aliens starting on Saturday after getting laid off or fired on Friday. People have to file a Freedom of Information Act to get a receipt number of a step in a Green Card process to continue the process at different company if the previous employer refuses to give it to you.
It's not just me saying that, the Congressional Research Service has it in their report about removing country caps. If that happens then there is no reason for these companies to prefer hiring Indians over others. TLDR: The abuse that you speak of is the end result of the racist per country limits from 1964.
https://crsreports.congress.gov/product/pdf/R/R45447
>Others who favor eliminating the per-country ceiling contend that the current system
discriminates against some foreign workers based on their country of origin, a characteristic they
contend has little bearing on workers’ labor market contributions. Such proponents argue that the
current system effectively ties immigrant workers to the employers that sponsor them for
extended periods and invites potential exploitation. According to this perspective, employers who
petition on behalf of prospective employment-based immigrants have disproportionate power
over them. Because such employers can withdraw their petitions at will, they discourage foreign
workers from negotiating for higher wages and/or improved working conditions.55 All else being
equal, rational employers therefore benefit financially by sponsoring such workers who remain
relatively immobile during their extensive waits to receive LPR status. Prospective immigrants
who consider leaving their employers face the prospect of effectively forfeiting their pending
employment-based immigrant petitions. If they cannot utilize another immigration pathway to
remain in the United States, they must return to their home countries.
In particular, Indian (and to a lesser extent Chinese and Filipino) nationals sit in much longer
queues of pending employment-based petitions submitted to USCIS and visa applications to DOS
than their counterparts from other countries.56 They consequently must wait the longest to obtain
LPR status. Those who favor eliminating the per-country cap contend that such circumstances
effectively encourage employers to sponsor prospective employment-based immigrants primarily
from India.57 According to this perspective, de facto discrimination results on the basis of origin
country, fostered partly by U.S. laws which otherwise prohibit most forms of labor market
discrimination. The more that employers follow this hiring approach, the greater the queue of
Indian prospective immigrants and the longer the waiting times for acquiring LPR status, creating
a self-reinforcing cycle that may limit hiring of prospective employment-based immigrants from
other countries.
Proponents argue, therefore, that removing the per-country ceiling from employment-based
immigrants would “level the playing field” by making immigrants from all countries more
equally attractive to employers. If the per-country ceiling is eliminated and the current queue of
pending petitions and visas is processed, proponents argue, employers would have no incentive to
sponsor employment-based immigrants from any one country over others except based on
conventional labor market criteria. As a result, waiting times for prospective employment-based
immigrants to receive LPR status would ultimately equalize across countries of origin