Because it will change your perception about Bihar.
BODH GAYA is not what you will think about Bihar. There wont be bad roads, there wont be people eating pan and spitting on roads, there wont be narrow dark lanes, there wont be people chasing you to sell stuff. Its a different world and its serene.
Because there is 2300 yr old temple
You can the amazing work done 2300 yrs back (yes its not 20 or 200). The temple has its own pull and it is visited by tourist across the globe.
Because the stay options are cheap
You can get decent accommodation for 1000 bucks. This will make perfect choice if you are backpacking and exploring your spiritual side
Because you can join biggest group meditation exercise for free
The maha bodhi temple complex is visited by scores of people and many can be seen meditating there in different corners. Feel free to pick your corner and try to awaken Buddha in you.
Because there are dozens of Monastery.
You can get your fixation of Monastery completed here. There is Thai, Chinese, Japanese, Cambodian and many other monasteries here. Each one in unique in their own way. More are getting built. Feel free to explore them at your own ease.
Because you can see 80 ft Buddha
Star attraction of Bodh Gaya - An 80 ft giant buddha statue, sitting in lotus position can be seen here.
Because it can be combined with other historical places such as Vaishali ruins, Nalanda ruins etc.
Once you had your dose of Buddhism you can explore what the world looked like in Ashoka's time.
Enough to explore, so little time. START.