This can work as you have experienced. However, it can also cause issues if both antennas pick up the same transmitter. I suspect you are using directional antennas pointed in very different directions with lots of distance to the towers, so each antenna feed is only collecting usable signals in that specific direction. Picking up the same transmitter from 2 different antennas and then combining with a splitter can be problematic.
More sophisticated combiners like the Televes units don’t have these issues, because part of the digital capability (vs RF) allows very steep slope filtering between transmitter frequencies. What this allows is user-defined transmitter frequencies to be specified for each antenna feed. If 2 antennas are both receiving transmitter channel UHF 26, the user can choose which antenna feed to use (e.g. the “better” one), and filter out that same frequency from the other antenna. The TV (or Tablo) tuners will only “see” the preferred antenna feed for UHF 26 in a channel scan.
Another use of this functionality is if desired content is coming in on UHF 26 from 1 antenna, and UHF 29 from another antenna (say FOX and associated sub-channels), you can assign UHF 26 to come through from antenna 1, and simply don’t assign UHF 29 from antenna 2. Now your TV tuner only “sees” one instance of FOX and related sub-channels coming in on UHF 26 from antenna 1 on a channel scan. This avoids duplicates in channel scans.
This capability is particularly useful to me, where I am right between 2 different tower locations, and most major networks are duplicated on different RF frequencies from both locations. Even with a directional antenna, I still receive unwanted duplicates on different RF channels coming from the 2 locations. It’s a mess in the channel scans. I use the Televes unit to clean all of this up, and present just the transmitters I want to my TV tuners.
As previously pointed out, these devices are expensive. However, they can also be very useful in solving specific problems.