They become dead telephone poles. Do not do this. I repeat, do not do this. Unless you want to carve tikis out of the trunks...

any palm that suffers major damage to the top is almost always a gonner...

split in half is definetly a gonner :)

To get technical, solitary palms have meristematic activity only at the apical spear, unlike other plants or clumping palms that can grow new plant material at many different places.

When the meristem cells are killed (eg, cut off, lightning,) or die (old age, infections), the plant is not necessarily dead, but cannot grow anymore, so when the current foliage is exhausted/expires, the plant dies.

meristem definition from M-W Unabridged:

a formative plant tissue made up typically of small essentially isodiametric cells lacking prominent vacuoles and capable of an indefinite number of divisions and giving rise to initiating cells that remain meristematic and to derivatives that undergo differentiation to produce the various tissues and organs of the plant, all postembryonic growth depending ultimately on the proliferation of meristematic cells  compare CAMBIUM

That said, you may get one palm in a thousand that DOES resprout from a decapitated trunk, and the likelihood of that happening seems to vary from one species (or genus) to another.

I've an amazing palm I've had for over 30 years. Cut in half at the trunk, stuck in soil and have 3 amazing plants..... Confused now as to do this again., maybe I got lucky 3 times..🤔

Are you sure it's a palm? There are many plants that people call "palms" but are not palms. Post a photo and I'm sure it will be identified as not being a palm.