This is a result of:

* Single-core performance no longer dramatically improving - almost plateauing

* The rate or extent of "bells and whistles" and other OS overhead being added - decreasing.

* Budget consumer CPUs having reached smooth desktop performance (with sufficient memory and and an SSD) already, even with multiple applications open.

.. and all of these had not been the case during the 1980s, 1990s and 2000s. Now, if your machine's hardware doesn't brake down - and you're just a plain desktop user - your motivation for throwing away your machine is quite limited.

---

Of course, this is not the case for smartphones, we're still on the roller-coaster there.