It's almost all catering to local taste and what's expected. Nepali food is good but it's not as rich as what you'd get in a restaurant. Daal baht (rice with a thin lentil soup) is not what people expect if they pay $10-20. Hell, most northern indian restaurants feature foods that are way richer than you'd see in real home cooked cuisine. The restaurant versions invariably have way more heavy cream and butter than would ever be used in a typical home.