Why does the majority of smartphones only support MicroSD cards up to 32 Gb?
The majority of smartphones only support Micro SD cards up to 32 GB because This is enough memory of any phones and would be either a software limitation, song limitation, picture limitation, application limitation or the type of formatting used on the SD cards.
The SDHC specification is only up to 32GB. The memory addressing capacity of the controller (physically or firmware) is the limitation. If the phone can support SDXC (via native hardware support or firmware update of a SDHC controller capable of handling space addressing requirement of HDXC specification), then it will support more than 32GB.