You mean as opposed to never calling dlclose to the handle? If you specify RTLD_NODELETE, the dynamic linker can avoid some dependency tracking that would otherwise be needed to avoid premature unloading of the object because that unloading can never happen.
However, the main application of NODELETE is the DF_1_NODELETE flag in the shared object itself. A typical use case is if the shared object installs a function pointer somewhere where it cannot be reverted as part of the dlclose operation. If the dlclose proceeds despite this, calling the function later will have hard-to-diagnose, unpredictable consequences. Rather than relying on dlclose never being called (which is difficult because the object might have been loaded as an indirect dependency, unaware to the caller of dlopen), using the DF_1_NODELETE flag makes this explicit.
However, the main application of NODELETE is the DF_1_NODELETE flag in the shared object itself. A typical use case is if the shared object installs a function pointer somewhere where it cannot be reverted as part of the dlclose operation. If the dlclose proceeds despite this, calling the function later will have hard-to-diagnose, unpredictable consequences. Rather than relying on dlclose never being called (which is difficult because the object might have been loaded as an indirect dependency, unaware to the caller of dlopen), using the DF_1_NODELETE flag makes this explicit.