Then you wake up one day being steamrolled by business change where other senior dev with some business analyst hijacks process does some awful crap "because business needs this ASAP" and leaves you maintaining/fixing up pile of crap.
Guess who is blamed later on for the system is not up to standard like having security hole or totally not logical flow in places where "business need" was implemented. Keep in mind after 6 months no one will remember they did that business change everyone will remember that you are maintaining the system because you try to keep it decent so it is your fault ;)