I think some of it is the baby, they see the baby being carried & if touch is a love language then what better way to gain love than to be carried.
Also shoes are they comfortable? That can make a difference
Also worth consideration is DS1 will & always has walked everywhere but his respiratory fitness has never been as good as DS2, DS2 had the nickname for a long time of "run fast, walk slow" because he'd always rather run than walk BUT he'd rarely want to walk somewhere & "I'm tired" would come out. When he was 8 he suffered shin splints after the school Athletics Carnival (admittedly he did lots of events at hard pace) & it was then we found out that among other things he had very flat feet & because he is very tall the ligaments & muscles needed more stretching than was normal in an 8yo... most children don't need to stretch until they are pre teens, but DS2 needed to stretch before exercise at 8yo - I mean runner stretches. Once we got all that sorted he's been a great walker. So it might be worth digging around a bit & seeing if it hurts her feet or legs to walk too.
FWIW I always thought I was a lazy child because iI didn't like to walk much, but I never found it comfortable walking, even though I walked 25mins to the train each way & 10mins at the other end, I still never felt like it wasn't hard work on my legs - turns out it was probably a hip problem - although broken foot & child carrying on hip are the reason the physio found it, but I think it was just made worse. Now that I do some work on it I've noticed I'm better & also I spend $$$ on shoes & that makes a difference