I know this isn't new, but recently I've been seeing it impacting almost every connecting flight that I've booked.

UA seems to be frequently limiting availability on married segments as a way of charging more for shorter connections, relatively to longer ones.

For example, I'm looking at TLV-EWR-SFO in a few weeks. The obvious connection is the one with 2h10 between flights, however as a married segment this pair of flights is S9T7L1K0, so a minimum L fare for one passenger ($70 more than K), or S/T for two (doesn't appear to be a T fare filed). The 5h40 connection option is T9L4K1, and you need to go even longer before you get to K2 or higher. ie, the shorter, more convenient connection is more expensive than the longer connections, made worse if you're not travelling alone.

The underlying flights are completely different - S9T9L4K3 for the TLV-EWR, and S9T9L9K9 for all of the EWR-SFO flights. Splitting the married segments (ie, multi-city) happily books the lower through-fare K price on any of the connecting options. Even tools like ITA Software Matrix don't seem to find these potential splits.