Didn't start with the tech industry. If you were a kid in the 80s or 90s, the vast majority of parties were pizza parties. This was also the entire business model of Chuck E Cheeses, which ran a ubiquitous series of commercials in the 80s. Its popularity in late-night hackathons and meetups is likely a holdover from college (where pizza at events is also ubiquitous), which itself is a holdover from childhood.

The history of pizza in the U.S. is itself fascinating. It was largely limited to Italian immigrants until WW2, when soldiers returning from the Italian campaign developed a taste for it. It exploded in popularity afterwards, particularly from the 1960s onwards. This is perhaps related to it being easy to eat without utensils, which made it convenient in the car/drive-in culture of that time period.

I was also surprised to learn that the vast majority of pizza varieties in the U.S. are actually American inventions, and that pizza in Italy basically consists of two varieties: marinara and margherita. All this stuff about pesto pizzas, BBQ chicken pizzas, meat lover's pizza, broccoli pizza, Hawaiian pizza, etc. are North American (including Canadian) inventions.