Low cache and fsb. L2 cache on the celeron is 2.93 is 256 where as the p4's come 512 and most 1mb. Celeron FSB is 533 whereas the p4 is 800 and some 1066.
The Celeron is a budget processor, so it's not as fast and it doesn't have as much of a cache as the Pentium. Worse, it is normally crushed by the AMD Sempron, and tends to be more expensive. So if you want to build a budget machine, just get a Sempron 64 instead.
Intel Celeron 2.93 
Linear Mode
