There is no voice assistant module built into the Sonos Play: 5.
 

However using other hardware with either Alexa or Google Assistant installed, you can play/control some streaming music sources on that device and any other Sonos speaker using the Sonos Skill installed in the Amazon Alexa or Google Assistant Apps.

I fail to understand why top shelf products in the range do NOT have this capability.

My products are reaching software EOL and the equivalent products do not offer this yet the cheaper products do.

Some new products get Apple AirPlay.. wow, okay if you use Apple products.

I have some Play 5s, Amp and Connect, non of which have Google Assist in the NEW updated models.

I think it’s because they were all pre-smarthome development by Sonos. Perhaps we will see the voice assistant on the next generation and any new products. Those Sonos products you mention were built prior to Alexa ever appearing on the Sonos One and Beam.

I understand, but the replacement ones are the latest, although I do not know when they were released or developed.
For me, I will not spend money on them especially if they may be updated to include those features.
Plus, they still do not support HIGH Def Audio.

Pity.

Ah okay, well I hope you eventually get what you wish for.

All the best.