Bikes don't need justification, most people who own them ride a few times a year. Everyone got their reason for riding...for me it's the best shot of adrenaline to get you out of a slump or a shitty day. Unless you buy new or euro, they don't depreciate as quick as cars and anything under 10k almost hardly depreciates unless you whack a lot of km on it.
I'll be honest though, most people I know with a bike, myself included, are always in two minds...do I keep it or do I sell it. The latter when they aren't riding it, but when they are, they're thinking why the f**k would I get rid of this.