These are 4 situations in which we are excused from using water for Wudu. In other words, these are examples of when Tayammum (dry ablution) using earth is allowed as permitted by Allah (ﷻ).
Quran 4:43: "O you who have believed, do not approach prayer while you are intoxicated until you know what you are saying or in a state of janabah, except those passing through [a place of prayer], until you have washed [your whole body]. And if you are ill or on a journey or one of you comes from the place of relieving himself or you have contacted women and find no water, then seek clean earth and wipe over your faces and your hands [with it]. Indeed, Allah is ever Pardoning and Forgiving."
Qur'an 5:6: "O you who have believed, when you rise to [perform] prayer, wash your faces and your forearms to the elbows and wipe over your heads and wash your feet to the ankles. And if you are in a state of janabah, then purify yourselves. But if you are ill or on a journey or one of you comes from the place of relieving himself or you have contacted women and do not find water, then seek clean earth and wipe over your faces and hands with it. Allah does not intend to make difficulty for you, but He intends to purify you and complete His favor upon you that you may be grateful."
Saying "I cannot find water to do wudu and pray" or "water will make my sickness worse" or "I touched my wife but there is no water to purify myself for prayer" or "I was traveling and found no water nearby" is hence not an excuse because we can use the clean earth to purify and then pray.