Not everyone has the budget for enterprise hardware or the desire to learn how to configure it. Also, enterprise networks are typically designed to serve a large number (dozens to thousands) of devices all asking for a little bandwidth all the time while home networks typically only have to serve a dozen or so devices with generally only a few, maybe just one, using a lot of bandwidth at a time. 40MHz in the 2.4GHz band does not make sense in a large office since running two 20MHz APs instead yields better overall bandwidth for the network, but at home in a sparse neighborhood, it can boost performance. Hence some enterprise hardware doesn't even have the option for 40MHz in the 2.4GHz band, something I found out configuring an older Cisco AP for use at a family member's home.
Whether to use OpenWRT or DD-WRT is debatable, best to get hardware that supports both so you can try them out and go with whichever one you find better.