Pulling page view data with UTM queries using "first touch" and "last touch" - why so different?

[patriciae930080]

In pulling page view data for campaigns using UTMs, first touch (never expire)  and last touch (never expire) are very different, with last touch being greater, by triple in some instances. Why is that and which data set would be better when applying orders/purchase attribution? NOTE: Our organization does not have the Marketing Channels Reporting set up. Rather, the reports are built using segments created from UTM parameters.