I am very particular about how my suits fit. Sleeves must show a quarter inch of shirt cuff. Pants need a slight break only. Less room in the seat by far than one finds in the usual off-the-rack suit. But most important is that the jacket's waist fit reasonably close to my actual waist.
Of course, a tailor can't really futz with the jacket's front panels, so material must be taken out of the back. This leads to interesting results on suits with lots of vertical stripes.
Ah, well. Better than wearing a baggy jacket.