Why does the fear of missing the Funeral (Janazah) prayer permit Tayammum, while the fear of missing the daily Asr prayer does NOT?

Because Funeral prayer is a Fard Kifayah and Asr is Fard Ayn.
Because the Funeral prayer has no replacement or makeup (Qada'), while daily prayers can be made up.
Because Funeral prayer is shorter.
Because water is disliked during funerals.