When Civil partnerships were introduced as an idea, I initially supported them, but by the time they came into law, I objected, not on the ground of the rights they gave to gay couples, but because friends and siblings who were long term cohabitees (though not bed-partners) were specifically excluded.
And here's the upshot. An elderly sister will be slapped with 40% inheritance tax on their shared property once her sister dies. And in order to pay, she'll have to sell the home they have shared all their lives. All this whilst coming to terms in her 80s or 90s, with the death of a lifelong friend, sister and live-in companion.
If this isn't discrimination against celibacy, I don't know what is.