It is possible that they cannot take calls while at work and this avoids that. I have a friend who I can text at work and she can respond without getting into trouble but no calls allowed. Also for a while the reception inside the building she worked in was so bad you would not have been able to understand her speaking, but text messages got are (obviously) no problem.
However, that does kind of seem too good to be true. Lovely cow and both pictures look like pro shots.