Why should one write poems when one is old?

A rather lovely late sonnet by C H Sisson, from (to quote the Anecdotal Evidence blog, where I came across it) 'Nine Sonnets, a pamphlet not much thicker than a bookmark, printed by The Greville Press of Emscote Lawn, Warwick, in 1991'.

Why should one write poems when one is old?
Not, to be sure, in hope of reputation
Which has either come, or else will escape one.
In hope of love perhaps? But what is told
Now, will not strengthen anybody’s hold
On me or mine on them: the time of truth has come,
And yet I lie as I have always done
And leave myself and others unappalled.
Poets are liars, yet no more than others,
Those who are not their sisters are their brothers,
All of the same lying family,
Children of Adam, fond of all evasions,
Blaming, beguiling on the least occasions
And to the last, and so it is with me.

Something of my own mood, and feelings about writing, at the moment.