Why Mercury and Venus doesn't have moons? Please give a Scientific reason for it.

Dear student,
Please find below the answer:

The Mercury and Venus do not have moons because they are too close to the Sun. Any moon with too great a distance from these planets would be in an unstable orbit and be captured by the Sun. If they were too close to these planets they would be destroyed by tidal gravitational forces.  

Hope this clears your doubt.
Regards.