More than three-quarters (77%) of soy is used as feed for livestock.

https://ourworldindata.org/soy#more-than-three-quarters-of-global-soy-is-fed-to-animals

Soybean meal is not a byproduct of soybean production either. It's the main source of revenue

When we look at the most common extraction method for soybean oil (using hexane solvents), soybean meal is still the driver of demand

However, soybean meal is the main driving force for soybean oil production due to its significant amount of productivity and revenues

[...]

soybean meal and hulls contribute to over 60% of total revenues, with meal taking the largest portion of over 59% of total revenue

https://www.sciencedirect.com/science/article/abs/pii/S0926669017305010

This is even more true of other methods like expelling which is still somewhat commonly used

Moreover, soybean meal is the driving force for the whole process [expelling oil from soy] because it provides over 70% of the total revenue for soy processing by expelling

https://www.mdpi.com/2077-0472/9/5/87

Even other extraction methods being explored in research as well don't have soybean oil as the main driver of demand

From the results, soybean oil makes up around 24% of total revenues; revenue from insoluble fiber makes over 70%, due to the large amounts produced throughout the process. [of Enzyme-Assisted Aqueous Extraction]

https://www.researchgate.net/profile/Jasreen-Sekhon/publication/330375817_Economic_Feasibility_of_Soybean_Oil_Production_by_Enzyme-Assisted_Aqueous_Extraction_Processing/links/5c49d531a6fdccd6b5c586b6/Economic-Feasibility-of-Soybean-Oil-Production-by-Enzyme-Assisted-Aqueous-Extraction-Processing.pdf