If I was left a house in a Will, why do I have to pay the lawyer's and excector's fee?

Technically, the lawyer's and executor's fee is usually paid from assets of the estate.  If the only asset is a house, then there are little or no liquid assets from which to pay the fees.  Nonetheless, someone has to pay the fees.  If you inherit the house and wish to keep the house, you will have to pay the fees.

If the only asset of the estate is the house, I suggest you consult a probate and estate lawyer to see if that lawyer will negotiate a reasonable fee with you.  The lawyer can also work with the named executor to allow you to be appointed as executor so that fees are limited.