I have fond memories of piano-led sing-songs in pubs; I caught the tail-end of it in the 1970s, before the separate rooms were knocked into one and the pianos were replaced with jukeboxes and televisions.

Piano (electric or acoustic) is an asset to a session, whether instrumental or song-based, if played in tune by somebody who knows what they're doing (the same is true of banjo and bodhran/tambourine, if it comes to that). Always welcome from my point of view.