Question

why are union territories under the president

Answer 1

because of the two reasons
1-they cannot be joined by any state
2-they are not big enough to be state

so president looks after them

Answer 2

Answer:

Union territories are territories that are not a state, since they are either too small to be a state or are made Union territories owing to their special status and they are ruled directly by the government of the Nation, i.e. The Union Government or the Central Government. This ultimately leads the Union Territories to be under the President, as they have no particular form of government of their own to rule them.