Yea shoes can indeed be a point of interest as i mentioned. Anyway if one needs some motivation and fun goals in this aspect , can also be obssessed with the times / training methods used or even start training with the running groups (social aspect). These are far more sustained than buying, coz when the space hits the physical storage limit, then one would be out of luck liao.
it becomes an issue if the rate of purchase is > than the usage rate, and also exacerbated if weekly mileage is not high. I still have over 12 pairs of shoes in the cupboard despite stopped buying for like 3 years alr and even add a new 6 single rack tall shoe rack.......some pairs even chucked into the water/electrical riser due to shoe rack constraints.

Coz my wife also has a few pairs.
I am sure I am on the lower end of the spectrum and some have well over 50 pairs of shoes.