As Salam forum-ers,
[5:6] O you who believe, when you observe the Contact Prayers (Salat), you shall: (1) wash your faces, (2) wash your arms to the elbows, (3) wipe your heads, and (4) wash your feet to the ankles. If you were unclean due to sexual orgasm, you shall bathe. If you are ill, or traveling, or had any digestive excretion (urinary, fecal, or gas), or had (sexual) contact with the women, and you cannot find water, you shall observe the dry ablution (Tayammum) by touching clean dry soil, then rubbing your faces and hands. GOD does not wish to make the religion difficult for you; He wishes to cleanse you and to perfect His blessing upon you, that you may be appreciative.
If we are unclean due to sexual orgasm, we are needed to take a bath, but does this bath encompass in a broader sense readying oneself for salat? i am not sure.
It seems from the verse, that wudhu is a simplified bath which purpose is to make sure one is clean prior to salat. but if you have bathed due to being unclean, than it would suffice as though you have taken wudhu.
If you are clean, and bathed before salat, i think it should suffice as wudhu as well. What is important is the niat (intention)
People from the Prophets time did not really take bathes twice or thrice a day like in modern times. I think based on that, they were required to take wudhu before Salat just to make sure the important parts of the body as mentioned in the Quran, are cleansed.
Only my two cents worth. I still take wudhu before each prayer unless i just showered right before Salat especially maghrib and Isyak.
Love and Peace.