I want to know why is only Bitcoin in the limelight
Because it was the first cryptocurrency ever and one of the rare ones that actually solves a real problem and has a purpose.
I have someone that wants to invest in crypto but wants to invest in other coins he wants to know if other are same values as bitcoin and if other coins can be easily be exchanged or sell or for purchases.
Tell him to focus on bitcoin first and ignore altcoins because they are made for one purpose only, and that is to make their creators rich while bitcoin is created to give you financial freedom.