Overhead bin space is the big reason- give the somewhat (last 5 years-ish) changes to charging for the 1st checked bag, many who would have otherwise checked a bag are bringing on as carry-ons.
Many flights I've been on in past several years have had a real shortage of bin space, meaning getting on board early to make sure you're not the odd man out IS important (waiting for baggage carousel can take an extra 45 minutes)
Many flights I've been on in past several years have had a real shortage of bin space, meaning getting on board early to make sure you're not the odd man out IS important (waiting for baggage carousel can take an extra 45 minutes)