See Conacher 1988: 192 ad 947. "This deft `domestic' touch, inserted among the woes which drive Admetus outdoors, helps appropriately to lower the tone from the tragic to the `sordid-pathetic'." It does that and perhaps a little more. Dirty floors are something we might suppose Alcestis noticing. Admetus is realizing his loss by seeing what she would see. He is reviewing her life, noticing certain things for the first time. This is doubtless true of his thoughts about the people in her sphere, the wives of his friends, the children clinging to him, the servants (whom he noticed enough to browbeat or maybe even beat) are seen by him to have feelings, for her.