What are the reasons for this difference? Some thoughts...
- Buying someone else a drink is often a matter of convenience - only one person goes to the bar rather than several.
- There is an assumption that someone else will get the next round, so it evens out by the end of the night.
- People basically don't like receiving something for free, no strings attached.
- Food costs more than drinks, so people might think they 'owe' someone more.
Is it as simple as this?