Why is the first and last day only showing 75%?

The first and last day of any trip that a crewmember flies is considered a partial day.  All partial days are treated the same, and the verbiage in IRS Publication 463 states that they should be prorated 75% of the value of a full day for M&IE calculations.

Note that the way IRS Publication 463 is worded also alludes to the idea that using 100% for some crew members might be acceptable, although this is a controversial concept.  EZPerDiem defaults to 75% for partial days; however, if a crew member decides they want to use 100% on partial days, they can change that setting on the Tools & Settings Page.