Why electric supply in Aircraft is 115 V ,400 Hz though in houses is 230 V,50 Hz/110 V,60 Hz?

The major advantage of running an electrical system at 400 Hz rather than 50/60 Hz is that power supply becomes smaller in size and lighter in weight. Also area occupied by electrical machine is highly reduced. So smaller size and lighter weight is beneficial for aircraft as lighter weight and smaller size maximize the aircraft efficiency.

Now, the reason is clear for you.