Why do we have nightlatches in the UK?

[bumpyraker]

IMHO the typical nightlatch seen in the UK is next to useless. Most are poorly fitted non deadlocking ones that can be easily slipped.

So what is a history of the nightlatch? Why do we have the typical "nightlatch and mortice lock" setup as seen on many timber doors here in the UK?

Wikipedia https://en.wikipedia.org/wiki/Night_latch hints that it's a fire safety thing - the nightlatch is used at night and can be easily opened in the event of a fire.

Is that all there is too it? Why don't we just have a thumbturn on the back of a pin tumbler like a lot of other countries? Or a simple and strong sliding bolt?

Bumpyraker

[peterwn]

Probably habit and tradition. Worded or lever mechanism nightlatches predated pin tumbler nightlatches. One type of nightlatch had a key with a pivoting bit which moved 90 degrees when inserted. In more recent times higher quality nightlatches have a deadlatching arrangement and/or inside cylinder (often with only three pins).
Apart from domestic use, nightlatches were often used to augment security for doors with low security lever locks with limited number of differs or where masterkeys have been compromised or change keys filed down to masterkeys. Nightlatches are easy to install - a hole for the cylinder and a small amount of chisel work.
Walter Schlage's key in knob locks probably replaced nightlatches in USA but did not seem to be used in UK.
Different areas would have different traditions. For example if you want a high security in USA, you would probably be sold a Medeco, in Australia you would probably be sold a BiLock and in UK possibly a Mul-T-Lock or Abloy.