I'm just a softie for infants, babies, and toddlers. (They also bond with Grandpa if you are gentle, warm and soothing.) After that they begin to get heavy, learn the word No, and need bigger diapers. Mom often needs and appreciates more support in the early weeks, months and first couple of years.
16-20miles each way has given me a 32-40mile RT 'commute' by bike to babysit for 1/2 day for 2+years, since they relocated. Sometimes an overnight and 2 days with grandkids.
Earlier this month

photo by 4yo
In summer I take the longer route almost every trip.