…because people will buy it?
Consider the 3DS family: the 3DS showed up in 2010, then the 3DS XL appeared two years later in 2012. The 2DS came out a year later in 2013, as a weird half-step back targeted at kids. A more significant hardware revision in the form of the New Nintendo 3DS came out over the course of 2014 and 2015.
Similarly, the Xbox One came out in 2013 and 2014; the first revision (stripping out Kinect) launched mid-2014, with various configurations launching over the following years until the Xbox One X was first teased in 2016.
Arguably the Smash bundle could be considered an updated edition of the console, but I’d be very surprised if they didn’t also have some other hardware configurations to announce within the next six months.