Family practice
Pizza as a common birthday and celebration food
In the United States, United Kingdom, and other pizza-eating cultures, pizza is one of the most commonly chosen foods for children's birthday parties and informal celebrations — valued for being easy to order in bulk, agreeable to a mixed group of children and adults, and requiring no seating plan or plated service. This is a contemporary social convention rather than a historically old one: pizza's role as party food tracks its broader mainstreaming in the postwar United States rather than predating it.
The fuller page on this is What the evidence on shared meals actually supports.
What kind of claim this is
Contemporary common practice
Claimed only at this scope, not beyond it. How PizzaHQ scopes cultural claims
Where: United States
Also widely documented in the UK, Canada, and Australia; not evidenced as universal.
Related
Evidence
Supported, with regional variation- PizzaHQ editorial synthesis — PizzaHQ