In Arlington, the housing market is still relatively strong, but only for more modern units. So perfectly good older homes are torn down to make way for new, multi-unit developments, which can be sold at a premium. This one is located in a prime spot, just outside of Arlington Center.
A typical older Arlington single family goes for around $400,000. If you tear it down, you can build a two-family condo with each unit listing at upwards (sometimes well upwards) of $650,000.
Note how they’ve dug a two-family hole: