I've never read any DMG cover-to-cover, because invariably there are sections that I know I do not need to worry about right now and will only bother reading them at some later point if the need arises. And usually for a number of sections... those needs never arise.
Like in the 5E DMG, I've never needed to read things like the Sanity rules... most of the descriptions for things like siege weapons... the tables and charts to create random dungeons, etc. etc. And in fact, I'd say I skip over most random tables in all the various DMGs because I don't ever really pre-build random stuff. I either use pre-made things like modules or else I wing it during play and don't want to slow things down by rolling stuff up while we're playing.
Like in the 5E DMG, I've never needed to read things like the Sanity rules... most of the descriptions for things like siege weapons... the tables and charts to create random dungeons, etc. etc. And in fact, I'd say I skip over most random tables in all the various DMGs because I don't ever really pre-build random stuff. I either use pre-made things like modules or else I wing it during play and don't want to slow things down by rolling stuff up while we're playing.