My reason for not showering:

It's a chore for me!

I have to go downstairs to let the dogs out (and I watch my grandchildren most days)
Then I have to trudge upstairs
Decide what clothes to wear
Go in the bathroom and use the toilet, get the towel ready
Finally force myself to get into the shower
Then you have to get out and dry off, ugg
Dry my hair (I hate having wet hair)
Make it back downstairs
Then I collapse on the recliner because I'm exhausted!
It's like a chore

I shower like every 3 days. My daughter, also bipolar, showers about once a week.