[try_again]

Not really. Tests with two lines generally have one "control" line and one "test" line. If the control line fails to appear, then the result is invalid and you should try a new kit, regardless of what the other line said. If the control line appears, then the result is valid and the test line shows a negative (no line) or positive (line) result. So "pregnant" should only appear if both lines show up. It's a very simply boolean AND condition, but that's something that would be challenging to have done purely by chemical reaction. Probably a lot more complex than having a simple check by a circuit. Using a microprocessor, you can have "pregnant", "not pregnant" or "invalid" show up to give an unambiguous single result. Trying to achieve the same through chemical means only is likely also more prone to failure. Even if the outcome is clear, there are still false positives and negatives. Of course you should expect users to read the manual and be capable of interpreting a very simple system with only 4 combinations and 3 outcomes, but apparently that's beyond many people. Which is exactly why some test producers go to this length.