Liches *can* taste, touch, see, smell and hear just like any other characer (with the addition of improved undead senses, like darkvision). They can be skeletal sometimes, but just as often they can be described as gaunt and emaciated (not unlike the Iron Maiden pet undead, Eddie).
Liches don't have specific vulnerabilities, and can work on increasing their mystical power 24/7. No need to rejuvenate, hunt, drink blood, eat marrow, visit granny, suck brains with a straw or anything of the sort.
And who said liches have to live in a tomb? D&D's most famous lich, Azalin Rex, disguises his undead form with powerful illusions and is regarded by the people of Darkon as their (very) long-lived wizard-king Azalin, who lives in a spacious castle abode and is harsh, but just.
Te process of lichdom is something the character can do on his own, through mystical means. No need for another's bite (vampire), rely on embalmers *after your death* (mummy) or anything of the sort.