Although I realise that the majority of youngsters (put head on block here 
and state “under 40” as a broad ageist definition for the purpose of discussion only) have no serious interest in cheques. I accept that the generations are different. However I count amongst the older generation that still use them. They are slow, safe and secure. My peers and I all admit to not using them nearly as much these days, but acknowledge that they still have a value especially for posting and charities. There are many potential Monzo customers out there amongst the “over 40’s”. Is this a good case for having Monzo cheque books? I don’t know. Here is an independent website I found when researching the topic
www.chequeandcredit.co.uk
Like cash, cheques will be around for some time to come. The new scanning methods will avoid the need for presenting them live. It would surely be possible to have a facility for cheque scans (for processing cheques from other banks) in the Monzo app or via an email address, even if there were no plans for Monzo cheque books. Love to hear any thoughts on this from anyone out there including Monzo staff. You seem to consist mostly of “younger people” by my above definition. My overall impression is that you have no interest in including them in your future banking facilities. I could not find any major topics on this subject when I looked. Perhaps it is of no real interest or I simply didn’t find it? Thank you 
PS. It is honestly NOT my purpose to start an ageist discussion!!