There's the college girl who sort of finds religion and wants to wear the garb for a few years before she snaps out of it.
The lifelong Muslim is attracted to the simplicity. The enigmas and mysteries of the OT are steam ironed flat. The Quran works better as a cookbook. Some Christians try to treat the Bible as a recipe book, but that always leads to absurdities. So, true Christianity leads to greater richness, but also greater doubt. Islam is less challenging to understand.
Excellent observation. An inherent nexus exists between Judaism, Christianity, and Islam where each subsequent faith represents some form of revision upon the older ways. Jesus is a reformational figure, who pushed back against what he saw as fundamental errors in the theological development of the Jewish faith. His purpose was to correct those errors, and set straight the misguided teachings that had come to be embraced. Much of the resulting new religion reflects an improvement on the older Jewish theology. Where stoning woman for divorcing her husband proved to be a problematic theological principle, Jesus taught that the first stone should be thrown by a sinless person. Where the prohibition against doing work on the Sabbath might lead a person to starve, Jesus taught that the law must be read with flexibility and not be taken to extremes such that demand pain and suffering from the faithful.
Muhammad was also a reformational figure in nearly the exact same way. He set out to further clarify and refine perceived theological problems and inconsistencies within Christianity. As a result, there is a somewhat progressive transitional relationship between Judaism, Christianity, and Islam. An open minded and curious individual who comes from a Jewish background and who sets out to search for spiritual fulfillment can very naturally find themselves appreciating Christianity as a refinement of the imperfect Judaism that has left them unfulfilled. It's rather quite common for Jewish people to convert to Christianity their first introductions to Christian teachings. Likewise, an open minded and curious individual who comes from a Christian background and who sets out to search for spiritual fulfillment can very naturally find themselves appreciating Islam as a refinement of the imperfect Christianity that has left them unfulfilled; Christian to Muslim conversion occurs with the same ease for many people as Judaism to Christianity conversions.