Why are Lunar Eclipse more common than Solar Eclipse?
They aren't. Lunar eclipses and solar eclipses occur with almost equal frequency.
From http://eclipse.gsfc.nasa.gov/eclipse.html and pages within, there were / will be 11898 solar eclipses of all types and 12064 lunar eclipses of all types in the five millennia between 2000 BCE to 3000 CE. Lunar eclipses outnumber solar eclipses by less than 3% if you count eclipses of all types.
Of those 12064 lunar eclipses, 4237 were partial penumbral eclipses, in which at any one time only part of the Moon was in the Earth's penumbral shadow, and during the entirety of the event, none of the Moon entered the Earth's umbral shadow. These are extremely subtle eclipses, and because of this some people say they don't count as eclipses. If one discounts these partial penumbral lunar eclipses, then solar eclipses outnumber lunar eclipses by over 50%.
That's not quite fair because partial solar eclipses are also extremely subtle events. If one also discounts those partial solar eclipses, then solar eclipses (total, annular, and hybrid) slightly outnumber lunar eclipses (total and partial), but only by a mere 0.2%.
Another way to look at this is that lunar eclipses and solar eclipses occur with almost equal frequency.
However, for any one person, the odds of seeing a solar eclipse are rather small while the odds of seeing a lunar eclipse are quite large. One has to be willing and financially able to galavant around the globe to see solar eclipses. The path of totality of a solar eclipse covers but a tiny, tiny fraction of the Earth's surface. In comparison, about half of the Earth gets to see a total lunar eclipse.