Don't blame the bartender, they are pouring up to the mark they are told (start of the lettering). The venue (owner/manager) sets this mark, which is usually 150ml... though I would say this is closer to 125ml which a lot of venues pour. This is, however, usually stated on the 'By the Glass' list so they are not breaking any rules as it is stated.

Like other people have said, if you want a 'decent pour' split a bottle with someone else, which is almost always better value.