Academia tends to have fairly linear career paths. You do a doctorate, then maybe do a post-doc, then become a lecturer / assistant professor, etc. If you don't follow the path you end up without the track record (publications, funding, etc.) you need for promotion and will be passed over for other candidates who look more likely to succeed. There are many more applicants than positions in most fields.
If you're not on this career path, there is basically no alternative in most institutions. You can be an adjunct, or lab assistant, or other low-level employee forever but this will lead nowhere. This is particularly a problem in the US, where the tenure track system gives you seven years of grind to achieve tenure, and if you fail your academic career is basically over.
(Things are changing. Some institutions have, for example, teaching track positions.)
If you're not on this career path, there is basically no alternative in most institutions. You can be an adjunct, or lab assistant, or other low-level employee forever but this will lead nowhere. This is particularly a problem in the US, where the tenure track system gives you seven years of grind to achieve tenure, and if you fail your academic career is basically over.
(Things are changing. Some institutions have, for example, teaching track positions.)