Well thankfully, if you DO happen to really, really want XLR connections for some reason, Onkyo/Integra and Marantz are offering separate pre/pros now that are essentially just their top line receiver without built-in amps and a very slightly lower price tag! I don't think the small drop in price is anywhere equal to the savings in cost of not having any amps built in, but it's still a lot better than when pre/pros used to cost
more than their receiver cousin
That said, there really isn't anything that the Onkyo PR-SC5508/Integra DHC-80.2 or Marantz AV7005 offer that their counterpart Onkyo TX-NR5008/Integra DTR-80.2 or Marantz SR7005 do not. The processing is identical. The only differences are the built-in amps in the receivers and the XLR connections.
In my book, for almost everyone using these types of receivers/pre-pros, it makes more sense to just pay the extra $100 or so and get the receiver version. For the vast majority of people, these flagship receivers will flawlessly power their speakers. And for the handful of people with extremely low impedance or low efficiency speakers, or just massive rooms, there is still the entirely viable option to use the RCA pre-outs and add separate amps.
Cost-wise, it just makes more sense to allow the receiver to power the surround/height/width speakers while focusing any separate amplification on the front 3 speakers - and that is only if such separate amplification is even necessary!
The one case where I would say the pre-pro versions make more sense is if you are using self-powered speakers all around. For example, some people prefer to use professional studio monitors, and many of those are self-powered and also tend to use XLR connections. There's no reason why you cannot just use a simple RCA-to-XLR converter or cable, but if you are using self-powered speakers for all channels, it does make sense to save even just the $100 or so and opt for the pre-pro version.
Separate amps still make sense for certain situations, but for many people, they just aren't necessary. Especially with flagship receivers that have very capable amps built-in. I would have zero qualms about using a Denon AVR-4311 (or the upcoming 4312) or an Onkyo TX-NR5008 as the pre-amp section as well as the power section for the surround, surround back, and height/width speakers. I would also have zero qualms about using such receivers to power the front 3 channels as well in most situations with most speakers in most rooms. And for the far more rare circumstances where separate amplification does make sense, there is the entirely viable option to use a separate amp and the RCA pre-outs - either just for the front 2 or 3 speakers or for all 5-11 speakers in the setup.