That's a good question, and there are a few things behind the "why" that I didn't go into in the write up, including:

    - Enjoying taking classes
    - Interest in learning about breadth of material that I wasn't seeing as a FE eng (even at Google)
    - Some minor concern about having CS credentials (less these days, but very much a concern earlier in my career)
    - Interest in learning about academia and doing research

For me, there were enough intangibles that interested me, and importantly I didn't do it just for the career benefits, though I think it helped out (although with survivorship and confirmation bias, it's hard to say).

> in your late 20s/early 30s, it pays off more to put in the hours at work and to start a family in what’s left of your days

Another reason why I'm not continuing with the part-time studies! I've joked with my wife that in my free time, we _could_ have kids, or I could do a part-time PhD for 5 years...