Without trying to answer why, they appear to have discontinued 1/3 of their line if this source is accurate.

https://www.statista.com/statistics/804398/us-iphone-sales-b...

The 6s and SE were their last remaining headphone jack phones. Maybe they’re trying to force the wireless headphones change as well as pave a way for new models. The SE actually sold more this year. But adding it’s 8% made it a clear 33% model replacement.