Ultimately people do things they enjoy. People enjoy different things.
I love hosting groups of people at home. Yes, it's hard work, but it's satisfying. The meal planning, excitement of preparing the house, cooking, having a big party at home - I enjoy almost all of it.
Having a party at a restaurant is a totally different set of activities - it needs longer term organisation to book a date, work out exact numbers, maybe pay a deposit. When the meal's over, everyone goes home. Doing it with kids is much harder. There's a different set of societal expectations over payment (people are much less comfortable being paid for in a restaurant than eating food you've provided).
These are different sets of activities. Some people enjoy doing one set more. That's OK. From my point of view - I'm finally in the position in the last few years where I can host large parties at home, and I'm really happy about it. To me it's worth the cost.