It’s definitely difficult to be a chair umpire in modern times with all this technology if he does not have the help of the Hawkeye. In fact, if you do a mistake, that can be documented in many ways and then posted on social media.
Something incredible happened in Rome after Marton Fucsovic lost a match against Nikoloz Bashilashvili following a completely wrong call from Gianluca Moscarella that is usually an excellent and passionate chair umpire.
The Georgian had 4 consecutive match points against Marton, and he committed a double fault on his first. The second serve was called out, but the chair umpire overruled the call to concede the repetition of the point. The odd thing is that there was a huge and clear mark on the court to make it clear that that serve was completely out.
Bashilashvili ended up winning that point (and the match), and Fucsovic was right in not being happy about that to take a picture and post it on social media.
Shapovalov about using the Hawkeye on clay
Denis was among the people that were horrified by what has happened also to state that there is the need of the Hawkeye even on clay to avoid this kind of episodes
Why the Hawkeye is not used on clay
The original reason for not using the Hawkeye on clay was that the surface is uneven and therefore the system should not be as precise as it is when used on hard courts. However, the most plausible reason is that the cost of the Hawkeye is very high and therefore the tournament organizations prefer checking the marks “as per tradition,” but then you can end up with these sort of horrific mistakes.