//People drink from water bottles & soft drinks bottles all the time - is that uncivilised?//
Yes. Eating and drinking in the street at all is uncivilised and if you’re indoors you can use a respectable receptacle.
//Were you to take a bottle of lager from the fridge and pour it into a glass, you would immediately raise the temperature of the lager. which would be a mortal sin.//
It wouldn’t be a mortal sin. But it would, in the case of many lagers produced by the large brewers, make the liquid virtually undrinkable. Those lagers – especially the one that is “probably the best lager in the world” – are only palatable at temperatures low enough so that no flavour can be determined. Of course if this truly is the reason for not using a glass you could always keep a glass in the fridge. As mentioned, many decent bars do so.
Bottles are for transporting the liquid from where it is produced to the end user. They are not designed as drinking vessels. For no other reason the neck is not wide enough to allow air in to the bottle to replace the lost liquid and atmospheric pressure tries to force air into the bottle whilst the drinker is drinking from it making it a most uncomfortable experience.
This habit seemed to develop about 20-25 years ago. It has been said to me that it is to prevent "spiking". I can only say that people should be more choosy where they drink and who they drink with. It is an absolutely filthy practice. Even bottles that are sold in multi packs are subject to dust and grime and a lot more besides. Imagine if you were given a drinking glass that had come straight from the manufacturers, been carted about in a dusty cardboard box in lorries and vans, been handled by multiple people and then you were expected to place it in your mouth. Would you do that when the glass looked dusty, grimy and was covered in finger marks? No, thought not.