Hi Ali - some sinks care about the amplitude, and others do not.
For example, the instruments built into gnuradio (Scope, Frequency display, etc.) can examine a signal of almost any amplitude within floating-point range because you can adjust the display scale factor.
However other sinks, such as a physical transmitter (USRP, HPSDR, etc.) are constrained in the amplitude that they can accept. Normally this must be less than one, and hitting or exceeding 1.00 (even just on the peak) can cause problems. Also a physical transmitter might have only 12 or 16 bits fixed point dynamic range, so there may be a minimum signal amplitude as well.