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that's the beauty of the bicycle.
On every big ride i've been on, there's been some guy on a one speed, or a unicycle or even a hotwheels plastic bike going down the road with us.
You don't NEED the fanciest coolest bike. For MTB'ing there's a lot of stuff you can do with your cheap old bike. But it will be easier with the newer lighter fancier one.
The same with things like tribikes. you don't NEED a special tribike for a triathlon, but it might shave some seconds off your ride.

are you wanting a new bike? have some fun. go look around. maybe you'll fall in love!