Why do some babies have more gas than others?

They cry more: Gas! in babies, it comes from swallowing air while drinking milk and while crying. It comes back out as a burp, or it travels thru the gut and comes out the other end as flatus. "gas" doesn't cause crying, colic or fussiness. Conversely, crying causes "gas". Immaturity causes crying, some babies are more immature than others, they cry more, thus, they have more "gas". It goes away after 3 months.

Digestive issues: Babies are born with all systems in tact but not fully mature. Many enzymes needed for digestion are not mature until 6-9 months. Many babies are also not colonized with beneficial bacteria in the birth process, and good bacteria aid in digestion.All these can lead to poor fermentation and digestion of food and hence more gas.