I have seen this firsthand. I haven't gone to law school yet, but I can assure you even if I am top 5% of my class, I will not be working at Big Law after graduation.
You say that now...
This is how it works for many:
The debt starts piling up, career services will urge you to do OCI just to see. A firm offers you 40k to spend the summer going out to eat. You say, "why not, it's just a summer." They give you an offer. You won't have another offer ready to go for months in the best case. Any other offer will be for less than 1/2 the money. You take the biglaw offer thinking "just for a while, until the debt is paid off".
Alternative situation: You don't rank high enough. You confidently say you never wanted biglaw anyways.
Oh, really. What type of work do you want to do, and how did you decide that you wanted to do this for a career?
Ideally M&A tax planning. My offer is just for unspecified transactional work. If not tax, I will probably be in financial restructuring/bankruptcy (which I wouldn't mind either). I decided to go this route because I love technical complexity and am more drawn to the role of a lawyer as counselor (as opposed to advocate). The vast majority of small firm or government jobs are more litigation focused.