My mother has two doors in her house with missing or cracked glass.

They are old doors and it appears the rebates are a bit shallow for thick
glass.

Do we in fact need thick glass to be fitted, given that for safety we can
now use laminated, toughened, or film coated glass? To fit thicker glass
would mean replacing the doors.

Does it today need to be thicker to be strong enough not to break under its
own weight or something?

Or are all the safety glasses intrinsically thicker?

My Mother has been told by her usual builder that plain glass is OK thinner
where obscure is not. Is this because it can be thinner for the same
strength? Or is patterend intrinsically thicker?

thanks